grit_lib/porcelain/

hunk_select.rs

//! Select structured diff hunks by stable id and apply them to the index.

use std::borrow::Cow;
use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
use std::fs;
use std::str::FromStr;

use thiserror::Error;

use crate::apply::parse_patch;
use crate::apply::{
    apply_hunks_to_blob, apply_patch_to_index, apply_patch_to_index_and_write, ApplyOptions,
    FilePatch, Hunk, HunkLine, IndexApplyOptions, IndexApplyOutcome,
};
use crate::crlf::worktree_conversion_is_identity;
use crate::diff::hunk_id::{hunk_ids, hunk_ids_with_duplicate_peers, DiffSide, HunkId};
use crate::diff::structured::{
    structured_file_diff, SideBytes, StructuredHunk, StructuredLine, StructuredLineKind,
    StructuredSegment,
};
use crate::diff::{
    collect_files_for_target, imara_unified_hunk_slices, include_file_in_diff,
    read_worktree_side_bytes_for_diff, unified_hunk_body_for_diff_options,
    unstaged_file_diffs_with_peer_hunks, unstaged_raw_changes_with_peer_hunks,
    unstaged_raw_changes_with_peer_hunks_in, DiffOptions, DiffStatus, DiffTarget, FileChange,
    FileDiff,
};
use crate::error::{ApplyError, Error};
use crate::index::{Index, IndexLock, MODE_EXECUTABLE, MODE_GITLINK, MODE_REGULAR};
use crate::objects::FileMode;
use crate::objects::ObjectKind;
use crate::porcelain::checkout::{
    remove_empty_parent_dirs, smudge_bytes_for_worktree_path, write_smudged_blob_to_worktree,
    write_to_worktree_cached, LeadingDirCache,
};
use crate::porcelain::index_from_tree::refresh_stage0_index_stats_for_paths;
use crate::progress::{poll_cancel, Cancel, ProgressPhase, ProgressSink};
use crate::repo::Repository;
use crate::worktree_rules::WorktreeRules;

/// New-side line range for partial hunk staging (1-based, inclusive).
///
/// Line numbers match `grit diff --json` `lines[].new` on the unstaged side.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct LineRange {
    /// Repository-relative path.
    pub path: String,
    /// First new-side line number in the range (1-based).
    pub start: usize,
    /// Last new-side line number in the range (1-based, inclusive).
    pub end: usize,
}

/// Selected hunks by stable id and/or new-side line ranges.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct HunkSelection {
    /// Stable hunk ids from `grit diff --json` (`hunks[].id`).
    pub ids: Vec<HunkId>,
    /// Partial selections by new-side line number (`diff --json` `lines[].new`).
    pub ranges: Vec<LineRange>,
}

/// Failure while resolving or staging hunk ids.
#[derive(Debug, Error)]
pub enum HunkSelectError {
    /// Id string is not 12 lowercase hex characters.
    #[error("unknown hunk id {id}")]
    UnknownId {
        /// Raw id token from the caller.
        id: String,
    },
    /// Id is well-formed but no longer present on the requested side.
    #[error("stale hunk id {id}")]
    StaleId {
        /// The requested id.
        id: HunkId,
        /// Path when the caller narrowed the diff (or a single candidate file).
        path: Option<String>,
        /// Current ids on the same path when cheap to compute.
        current_ids: Vec<HunkId>,
    },
    /// Id belongs to the other index/worktree side (for example staged vs unstaged).
    #[error("hunk id {id} is for the {actual_side} side, not {requested_side}")]
    WrongSide {
        /// The requested id.
        id: HunkId,
        /// Side the id was computed for.
        actual_side: DiffSide,
        /// Side the caller requested.
        requested_side: DiffSide,
    },
    /// Hunks can only be selected on [`DiffSide::Unstaged`] or [`DiffSide::Staged`].
    #[error("hunks cannot be selected on the {side} side")]
    UnselectableSide {
        /// Side the caller requested.
        side: DiffSide,
    },
    /// Binary paths cannot be partially staged by hunk id.
    #[error("binary file {path} has no selectable hunks")]
    Binary {
        /// Repository-relative path.
        path: String,
    },
    /// Index apply failed after hunk resolution.
    #[error("{0}")]
    Apply(#[from] ApplyError),
    /// Line range lies outside the file's new-side line count.
    #[error("line range {start}-{end} is out of bounds for {path} (file has {max_line} lines)")]
    RangeOutOfBounds {
        /// Path named in the range.
        path: String,
        /// Range start (1-based).
        start: usize,
        /// Range end (1-based).
        end: usize,
        /// Last valid new-side line number.
        max_line: usize,
    },
    /// Range does not select any additions or deletions.
    #[error("line range selects nothing on {path}")]
    RangeSelectsNothing {
        /// Path named in the range.
        path: String,
    },
    /// Submodule (gitlink) entries cannot be restored hunk by hunk.
    #[error("submodule {path} cannot be restored by hunk")]
    Gitlink {
        /// Repository-relative path of the gitlink.
        path: String,
    },
    /// A diff reported a file mode that is not an octal Git mode.
    #[error("invalid file mode {mode} for {path}")]
    InvalidMode {
        /// Repository-relative path.
        path: String,
        /// The mode text as reported by the diff.
        mode: String,
    },
    /// A patch passed in for restoring names neither an old nor a new path.
    #[error("patch names no path")]
    MissingPath,
    /// Repository or diff engine failure (not a hunk-id selection error).
    ///
    /// Match on the boxed [`crate::error::Error`] to branch on the underlying failure, for
    /// example [`crate::error::Error::RequiresWorkTree`] when the repository is bare.
    #[error(transparent)]
    Repository(Box<Error>),
    /// Selected hunks could not be turned into an apply patch.
    #[error("could not build patch for selected hunks")]
    PatchBuild,
    /// Caller cancelled before the index was written.
    #[error("operation cancelled")]
    Cancelled,
}

impl From<Error> for HunkSelectError {
    fn from(err: Error) -> Self {
        HunkSelectError::Repository(Box::new(err))
    }
}

/// Result of [`stage_hunks`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct StageHunksOutcome {
    /// Whether this was a dry run.
    pub dry_run: bool,
    /// Staged ids per path (repository-relative).
    pub staged_hunks: BTreeMap<String, Vec<HunkId>>,
    /// Staged line ranges per path when line-range selection was used (`start` or `start-end` strings).
    pub staged_lines: BTreeMap<String, Vec<String>>,
    /// Index paths touched by the apply engine.
    pub added: Vec<String>,
    /// Paths updated in the index.
    pub modified: Vec<String>,
    /// Paths removed from the index.
    pub removed: Vec<String>,
}

impl StageHunksOutcome {
    fn from_apply(
        dry_run: bool,
        staged_hunks: BTreeMap<String, Vec<HunkId>>,
        staged_lines: BTreeMap<String, Vec<String>>,
        apply: IndexApplyOutcome,
    ) -> Self {
        Self {
            dry_run,
            staged_hunks,
            staged_lines,
            added: apply.added,
            modified: apply.modified,
            removed: apply.removed,
        }
    }
}

/// Unstaged file diffs with staged peer hunks on the same path (for id assignment).
///
/// # Errors
///
/// Propagates diff and repository errors.
pub fn unstaged_file_diffs(
    repo: &Repository,
    pathspecs: &[String],
) -> std::result::Result<Vec<(FileDiff, Vec<StructuredHunk>)>, Error> {
    let opts = DiffOptions::from_config(repo.config()?.as_ref());
    let (files, peers) = unstaged_file_diffs_with_peer_hunks(repo, pathspecs, opts)?;
    Ok(files
        .into_iter()
        .map(|f| {
            let peer = peers.get(&f.path).cloned().unwrap_or_default();
            (f, peer)
        })
        .collect())
}

/// Parse comma-separated or repeated id tokens into a [`HunkSelection`].
///
/// # Errors
///
/// Returns [`HunkSelectError::UnknownId`] for malformed tokens.
pub fn parse_hunk_id_list(
    tokens: &[String],
) -> std::result::Result<HunkSelection, HunkSelectError> {
    let mut ids = Vec::new();
    for token in tokens {
        for part in token.split(',').map(str::trim).filter(|s| !s.is_empty()) {
            ids.push(
                HunkId::from_str(part).map_err(|_| HunkSelectError::UnknownId {
                    id: part.to_string(),
                })?,
            );
        }
    }
    Ok(HunkSelection {
        ids,
        ranges: Vec::new(),
    })
}

/// Resolve `selection` on `side` to index-ready [`FilePatch`] rows.
///
/// Recomputes the live diff only for unstaged paths (optionally filtered by `pathspecs`).
/// Each path's id set uses the same peer-aware rules as `grit diff --json`.
///
/// # Errors
///
/// See [`HunkSelectError`].
pub fn resolve_selection(
    repo: &Repository,
    side: DiffSide,
    selection: &HunkSelection,
    pathspecs: &[String],
    diff_options: DiffOptions,
) -> std::result::Result<Vec<FilePatch>, HunkSelectError> {
    // Returns index-ready patches; see [`resolve_selection_with_staged`] for staged id map.
    Ok(resolve_selection_with_staged(repo, side, selection, pathspecs, diff_options)?.patches)
}

/// A selection resolved against the live diff: the patches to apply plus, per path, which hunk
/// ids and line range labels they came from.
#[derive(Debug, Clone, Default)]
pub(crate) struct ResolvedSelection {
    pub(crate) patches: Vec<FilePatch>,
    pub(crate) selected_hunks: BTreeMap<String, Vec<HunkId>>,
    /// Line range labels (`start` or `start-end`) per path.
    pub(crate) selected_lines: BTreeMap<String, Vec<String>>,
    /// Paths whose every hunk was selected by id, so reversing the patch can bring the file back
    /// to the content it was diffed against. Any other selected path keeps a difference.
    pub(crate) whole_files: BTreeSet<String>,
}

/// Resolve `selection` on the unstaged side, keeping the per-path ids and line labels that
/// [`resolve_selection`] drops.
///
/// # Errors
///
/// Same as [`resolve_selection`].
pub(crate) fn resolve_unstaged_selection(
    repo: &Repository,
    selection: &HunkSelection,
    pathspecs: &[String],
) -> std::result::Result<ResolvedSelection, HunkSelectError> {
    let diff_opts = diff_options_for_hunk_select(repo)?;
    resolve_selection_with_staged(repo, DiffSide::Unstaged, selection, pathspecs, diff_opts)
}

fn merge_resolved(into: &mut ResolvedSelection, other: ResolvedSelection) {
    for (path, ids) in other.selected_hunks {
        into.selected_hunks.entry(path).or_default().extend(ids);
    }
    for (path, ranges) in other.selected_lines {
        into.selected_lines.entry(path).or_default().extend(ranges);
    }
    into.whole_files.extend(other.whole_files);
    for patch in other.patches {
        if let Some(existing) = into
            .patches
            .iter_mut()
            .find(|p| p.effective_path() == patch.effective_path())
        {
            existing.hunks.extend(patch.hunks);
            existing.hunks.sort_by_key(|h| (h.new_start, h.old_start));
        } else {
            into.patches.push(patch);
        }
    }
}

fn resolve_selection_with_staged(
    repo: &Repository,
    side: DiffSide,
    selection: &HunkSelection,
    pathspecs: &[String],
    diff_options: DiffOptions,
) -> std::result::Result<ResolvedSelection, HunkSelectError> {
    resolve_selection_in(repo, None, side, selection, pathspecs, diff_options)
}

/// [`resolve_selection_with_staged`], resolving unstaged hunk ids against `index` when the
/// caller already holds the repository's index (it is loaded otherwise).
fn resolve_selection_in(
    repo: &Repository,
    index: Option<&mut Index>,
    side: DiffSide,
    selection: &HunkSelection,
    pathspecs: &[String],
    diff_options: DiffOptions,
) -> std::result::Result<ResolvedSelection, HunkSelectError> {
    if selection.ids.is_empty() && selection.ranges.is_empty() {
        return Ok(ResolvedSelection::default());
    }
    // Ids and patches only use line text, so intra-line emphasis would be computed for nothing.
    let opts = diff_options.with_word_level_inline(false);
    let requested: HashSet<HunkId> = selection.ids.iter().cloned().collect();

    match side {
        DiffSide::Unstaged => {
            // An index loaded here is dropped before the per-file diffs below.
            let (changes, peer_hunks) = match index {
                Some(index) => {
                    unstaged_raw_changes_with_peer_hunks_in(repo, index, pathspecs, opts.clone())?
                }
                None => unstaged_raw_changes_with_peer_hunks(repo, pathspecs, opts.clone())?,
            };
            let mut resolved = if requested.is_empty() {
                ResolvedSelection::default()
            } else {
                resolve_unstaged(
                    repo,
                    &changes,
                    &peer_hunks,
                    pathspecs,
                    opts.clone(),
                    &requested,
                )?
            };
            if !selection.ranges.is_empty() {
                let line_part = resolve_line_ranges_unstaged(
                    &changes,
                    &peer_hunks,
                    &opts,
                    selection,
                    &requested,
                )?;
                merge_resolved(&mut resolved, line_part);
            }
            Ok(resolved)
        }
        DiffSide::Staged => {
            if !selection.ranges.is_empty() {
                return Err(HunkSelectError::RangeSelectsNothing {
                    path: selection.ranges[0].path.clone(),
                });
            }
            resolve_staged(repo, pathspecs, opts, &requested)
        }
        DiffSide::Other => Err(HunkSelectError::UnselectableSide { side }),
    }
}

fn resolve_staged(
    repo: &Repository,
    pathspecs: &[String],
    opts: DiffOptions,
    requested: &HashSet<HunkId>,
) -> std::result::Result<ResolvedSelection, HunkSelectError> {
    let files = collect_files_for_target(repo, &DiffTarget::IndexVsHead, pathspecs, opts)?;
    resolve_on_files(
        DiffSide::Staged,
        files,
        HashMap::new(),
        requested,
        pathspecs,
    )
}

fn resolve_unstaged(
    repo: &Repository,
    changes: &[FileChange],
    peer_hunks: &HashMap<String, Vec<StructuredHunk>>,
    pathspecs: &[String],
    opts: DiffOptions,
    requested: &HashSet<HunkId>,
) -> std::result::Result<ResolvedSelection, HunkSelectError> {
    let mut patches = Vec::new();
    let mut staged_hunks = BTreeMap::new();
    let mut whole_files = BTreeSet::new();
    let mut found = HashSet::new();

    for change in changes {
        if change.binary {
            continue;
        }
        let peer = peer_hunks
            .get(&change.path)
            .map(|h| h.as_slice())
            .unwrap_or(&[]);
        let resolved = resolve_file_change_by_unified_body(
            DiffSide::Unstaged,
            change,
            peer,
            requested,
            &opts,
        )?;
        found.extend(resolved.matched);
        if let Some(staged) = resolved.selected_ids {
            staged_hunks.insert(change.path.clone(), staged);
        }
        if resolved.whole_file {
            whole_files.insert(change.path.clone());
        }
        patches.extend(resolved.patches);
    }

    let missing: Vec<HunkId> = requested
        .iter()
        .filter(|id| !found.contains(*id))
        .cloned()
        .collect();
    if let Some(id) = missing.first().cloned() {
        if let Some(wrong) = find_id_on_staged_side(repo, pathspecs, opts.clone(), requested)? {
            return Err(HunkSelectError::WrongSide {
                id: wrong,
                actual_side: DiffSide::Staged,
                requested_side: DiffSide::Unstaged,
            });
        }
        if pathspecs.len() == 1 {
            let path = &pathspecs[0];
            if changes.iter().any(|c| c.path == *path && c.binary) {
                return Err(HunkSelectError::Binary { path: path.clone() });
            }
        }
        let files: Vec<FileDiff> = changes
            .iter()
            .filter(|c| !c.binary)
            .map(|c| build_file_diff(c, &opts))
            .collect();
        let current_ids = current_ids_for_stale(DiffSide::Unstaged, pathspecs, &files, peer_hunks);
        return Err(HunkSelectError::StaleId {
            id,
            path: stale_path_hint(pathspecs, &files),
            current_ids,
        });
    }

    Ok(ResolvedSelection {
        patches,
        selected_hunks: staged_hunks,
        selected_lines: BTreeMap::new(),
        whole_files,
    })
}

fn side_text(bytes: &SideBytes) -> Cow<'_, str> {
    if bytes.data.is_empty() {
        return Cow::Borrowed("");
    }
    match std::str::from_utf8(&bytes.data) {
        Ok(text) => Cow::Borrowed(text),
        Err(_) => Cow::Owned(String::from_utf8_lossy(&bytes.data).into_owned()),
    }
}

fn line_count(text: &str) -> usize {
    let newlines = memchr::memchr_iter(b'\n', text.as_bytes()).count();
    if text.is_empty() || text.ends_with('\n') {
        newlines
    } else {
        newlines + 1
    }
}

/// One file's hunks matched against the requested ids.
struct UnifiedHunkResolve {
    /// The patch of the selected hunks (empty when none matched).
    patches: Vec<FilePatch>,
    /// Selected ids in hunk order, when any matched.
    selected_ids: Option<Vec<HunkId>>,
    /// Requested ids found on this file.
    matched: HashSet<HunkId>,
    /// Whether every hunk of the file was selected.
    whole_file: bool,
}

fn resolve_file_change_by_unified_body(
    side: DiffSide,
    change: &FileChange,
    peer_hunks: &[StructuredHunk],
    requested: &HashSet<HunkId>,
    diff_options: &DiffOptions,
) -> std::result::Result<UnifiedHunkResolve, HunkSelectError> {
    let old_text = side_text(&change.old_bytes);
    let new_text = side_text(&change.new_bytes);
    let body =
        unified_hunk_body_for_diff_options(old_text.as_ref(), new_text.as_ref(), diff_options);
    let before_count = line_count(old_text.as_ref());
    let after_count = line_count(new_text.as_ref());
    let before_ends_nl = old_text.as_ref().ends_with('\n');
    let after_ends_nl = new_text.as_ref().ends_with('\n');
    let slices = imara_unified_hunk_slices(&body);
    let ids = crate::diff::hunk_id::hunk_ids_for_unified_slices(
        side,
        &change.path,
        &slices,
        before_count,
        after_count,
        before_ends_nl,
        after_ends_nl,
        peer_hunks,
    );
    let mut selected_slices = Vec::new();
    let mut staged_ids = Vec::new();
    let mut matched = HashSet::new();
    for (slice, id) in slices.iter().zip(ids.iter()) {
        if requested.contains(id) {
            selected_slices.push(*slice);
            staged_ids.push(id.clone());
            matched.insert(id.clone());
        }
    }
    if selected_slices.is_empty() {
        return Ok(UnifiedHunkResolve {
            patches: Vec::new(),
            selected_ids: None,
            matched,
            whole_file: false,
        });
    }
    let whole_file = selected_slices.len() == slices.len();
    let patch = file_patch_from_unified_slices(change, &selected_slices)?;
    Ok(UnifiedHunkResolve {
        patches: vec![patch],
        selected_ids: Some(staged_ids),
        matched,
        whole_file,
    })
}

fn file_patch_from_unified_slices(
    change: &FileChange,
    slices: &[&str],
) -> std::result::Result<FilePatch, HunkSelectError> {
    let path = &change.path;
    let is_new = change.old_mode == FileMode::ABSENT;
    let mut is_deleted =
        matches!(change.status, DiffStatus::Deleted) || change.new_mode == FileMode::ABSENT;
    let is_rename = matches!(change.status, DiffStatus::Renamed);
    let is_copy = matches!(change.status, DiffStatus::Copied);
    if !is_new && !is_deleted && side_text(&change.new_bytes).trim().is_empty() {
        let preimage = side_text(&change.old_bytes);
        if !preimage.trim().is_empty() {
            is_deleted = true;
        }
    }
    let mut text = format!("diff --git a/{path} b/{path}\n");
    if is_new {
        text.push_str(&format!("new file mode {}\n", change.new_mode));
    }
    if is_deleted {
        text.push_str(&format!("deleted file mode {}\n", change.old_mode));
    }
    let old = if is_new {
        "/dev/null".to_string()
    } else {
        format!("a/{}", change.old_path.as_deref().unwrap_or(path.as_str()))
    };
    let new = if is_deleted {
        "/dev/null".to_string()
    } else {
        format!("b/{}", path)
    };
    text.push_str(&format!("--- {old}\n+++ {new}\n"));
    for slice in slices {
        text.push_str(slice);
        if !slice.ends_with('\n') {
            text.push('\n');
        }
    }
    let mut patches = parse_patch(&text, 1, path, false, None).map_err(map_parse_err)?;
    let mut patch = patches.pop().ok_or(HunkSelectError::PatchBuild)?;
    patch.is_new = false;
    patch.is_deleted = is_deleted;
    patch.is_rename = is_rename;
    patch.is_copy = is_copy;
    patch.old_path = if is_new {
        None
    } else {
        change.old_path.clone().or_else(|| Some(path.clone()))
    };
    patch.new_path = if is_deleted { None } else { Some(path.clone()) };
    patch.old_mode = Some(change.old_mode.to_string());
    patch.new_mode = Some(change.new_mode.to_string());
    Ok(patch)
}

fn build_file_diff(change: &FileChange, opts: &DiffOptions) -> FileDiff {
    let structured = structured_file_diff(
        change.old_mode,
        change.new_mode,
        &change.old_bytes,
        &change.new_bytes,
        opts.clone(),
    );
    FileDiff {
        path: change.path.clone(),
        old_path: change.old_path.clone(),
        status: change.status,
        old_mode: structured.old_mode,
        new_mode: structured.new_mode,
        old_oid: change.old_oid,
        new_oid: change.new_oid,
        binary: change.binary,
        content_changed: change.content_changed,
        old_encoding_lossy: structured.old_encoding_lossy,
        new_encoding_lossy: structured.new_encoding_lossy,
        hunks: structured.hunks,
        line_stat: None,
    }
}

fn find_id_on_staged_side(
    repo: &Repository,
    pathspecs: &[String],
    opts: DiffOptions,
    requested: &HashSet<HunkId>,
) -> std::result::Result<Option<HunkId>, HunkSelectError> {
    let files = collect_files_for_target(repo, &DiffTarget::IndexVsHead, pathspecs, opts)?;
    Ok(files.into_iter().find_map(|file| {
        if file.binary {
            return None;
        }
        hunk_ids(DiffSide::Staged, &file.path, &file.hunks)
            .into_iter()
            .find(|id| requested.contains(id))
    }))
}

fn resolve_on_files(
    side: DiffSide,
    files: Vec<FileDiff>,
    peer_hunks: HashMap<String, Vec<StructuredHunk>>,
    requested: &HashSet<HunkId>,
    pathspecs: &[String],
) -> std::result::Result<ResolvedSelection, HunkSelectError> {
    let mut found = HashSet::new();
    let mut patches = Vec::new();
    let mut staged_by_path: BTreeMap<String, Vec<HunkId>> = BTreeMap::new();

    for file in &files {
        if file.binary {
            continue;
        }
        let peer = peer_hunks
            .get(&file.path)
            .map(|h| h.as_slice())
            .unwrap_or(&[]);
        let ids = hunk_ids_with_duplicate_peers(side, &file.path, &file.hunks, peer);
        let mut selected = Vec::new();
        let mut selected_ids = Vec::new();
        for (hunk, id) in file.hunks.iter().zip(ids.iter()) {
            if requested.contains(id) {
                selected.push(hunk.clone());
                selected_ids.push(id.clone());
                found.insert(id.clone());
            }
        }
        if selected.is_empty() {
            continue;
        }
        staged_by_path.insert(file.path.clone(), selected_ids);
        patches.push(file_patch_from_hunks(file, &selected)?);
    }

    let missing: Vec<HunkId> = requested
        .iter()
        .filter(|id| !found.contains(*id))
        .cloned()
        .collect();
    if let Some(id) = missing.first().cloned() {
        if let Some(path) = stale_path_hint(pathspecs, &files) {
            if files
                .iter()
                .find(|f| f.path == path)
                .is_some_and(|f| f.binary)
            {
                return Err(HunkSelectError::Binary { path });
            }
        }
        let current_ids = current_ids_for_stale(side, pathspecs, &files, &peer_hunks);
        return Err(HunkSelectError::StaleId {
            id,
            path: stale_path_hint(pathspecs, &files),
            current_ids,
        });
    }

    Ok(ResolvedSelection {
        patches,
        selected_hunks: staged_by_path,
        selected_lines: BTreeMap::new(),
        whole_files: BTreeSet::new(),
    })
}

fn stale_path_hint(pathspecs: &[String], files: &[FileDiff]) -> Option<String> {
    if pathspecs.len() == 1 {
        return Some(pathspecs[0].clone());
    }
    if files.len() == 1 {
        return Some(files[0].path.clone());
    }
    None
}

fn current_ids_for_stale(
    side: DiffSide,
    pathspecs: &[String],
    files: &[FileDiff],
    peer_hunks: &HashMap<String, Vec<StructuredHunk>>,
) -> Vec<HunkId> {
    let path = stale_path_hint(pathspecs, files);
    let Some(path) = path else {
        return Vec::new();
    };
    let Some(file) = files.iter().find(|f| f.path == path) else {
        return Vec::new();
    };
    if file.binary {
        return Vec::new();
    }
    let peer = peer_hunks
        .get(&file.path)
        .map(|h| h.as_slice())
        .unwrap_or(&[]);
    hunk_ids_with_duplicate_peers(side, &file.path, &file.hunks, peer)
}

fn file_patch_from_hunks(
    file: &FileDiff,
    hunks: &[StructuredHunk],
) -> std::result::Result<FilePatch, HunkSelectError> {
    if file.binary {
        return Err(HunkSelectError::Binary {
            path: file.path.clone(),
        });
    }
    // Index preimage always comes from the existing stage-0 entry (including intent-to-add).
    let is_new = false;
    let is_deleted = matches!(file.status, DiffStatus::Deleted);
    let is_rename = matches!(file.status, DiffStatus::Renamed);
    let apply_hunks: Vec<Hunk> = hunks
        .iter()
        .enumerate()
        .map(|(i, h)| structured_hunk_to_apply_hunk(h, i + 1))
        .collect();
    Ok(FilePatch {
        diff_old_path: file.old_path.clone().or_else(|| Some(file.path.clone())),
        diff_new_path: Some(file.path.clone()),
        old_path: if is_new {
            None
        } else {
            file.old_path.clone().or_else(|| Some(file.path.clone()))
        },
        new_path: if is_deleted {
            None
        } else {
            Some(file.path.clone())
        },
        saw_old_header: true,
        saw_new_header: true,
        old_mode: file.old_mode.clone(),
        new_mode: file.new_mode.clone(),
        old_mode_line: None,
        new_mode_line: None,
        is_new,
        is_deleted,
        is_rename,
        is_copy: matches!(file.status, DiffStatus::Copied),
        similarity_index: None,
        dissimilarity_index: None,
        old_oid: None,
        new_oid: None,
        binary_patch: None,
        is_binary: false,
        hunks: apply_hunks,
        ws_rule: 0,
        is_toplevel_relative: true,
    })
}

fn merge_intervals(ranges: &[(usize, usize)]) -> Vec<(usize, usize)> {
    if ranges.is_empty() {
        return Vec::new();
    }
    let mut sorted = ranges.to_vec();
    sorted.sort_unstable_by_key(|(s, _)| *s);
    let mut out = vec![sorted[0]];
    for (start, end) in sorted.into_iter().skip(1) {
        if let Some(last) = out.last_mut() {
            if start <= last.1 + 1 {
                last.1 = last.1.max(end);
                continue;
            }
        }
        out.push((start, end));
    }
    out
}

fn line_in_intervals(line: usize, intervals: &[(usize, usize)]) -> bool {
    intervals
        .iter()
        .any(|(start, end)| line >= *start && line <= *end)
}

fn deletion_selected(removal_point: usize, intervals: &[(usize, usize)]) -> bool {
    intervals
        .iter()
        .any(|(start, end)| removal_point >= *start && removal_point <= *end + 1)
}

fn count_new_side_lines(bytes: &[u8]) -> usize {
    if bytes.is_empty() {
        return 0;
    }
    let mut count = bytes.iter().filter(|&&b| b == b'\n').count();
    if bytes.last() != Some(&b'\n') {
        count += 1;
    }
    count
}

fn new_side_line_count(change: &FileChange) -> usize {
    if matches!(change.status, DiffStatus::Deleted) {
        return 0;
    }
    count_new_side_lines(&change.new_bytes.data)
}

fn range_label(start: usize, end: usize) -> String {
    if start == end {
        format!("{start}")
    } else {
        format!("{start}-{end}")
    }
}

fn validate_line_ranges(
    path: &str,
    intervals: &[(usize, usize)],
    max_line: usize,
) -> std::result::Result<(), HunkSelectError> {
    for &(start, end) in intervals {
        if start == 0 || end == 0 || start > end || end > max_line {
            return Err(HunkSelectError::RangeOutOfBounds {
                path: path.to_string(),
                start,
                end,
                max_line,
            });
        }
    }
    Ok(())
}

fn filter_hunk_by_intervals(
    hunk: &StructuredHunk,
    intervals: &[(usize, usize)],
) -> Option<StructuredHunk> {
    let mut new_cur = hunk.new_start;
    let mut old_cur = hunk.old_start;
    let mut out_lines = Vec::new();
    let mut any_change = false;

    for line in &hunk.lines {
        match line.kind {
            StructuredLineKind::Context => {
                let new_n = line.new.unwrap_or(new_cur);
                let old_n = line.old.unwrap_or(old_cur);
                out_lines.push(line.clone());
                new_cur = new_n.saturating_add(1);
                old_cur = old_n.saturating_add(1);
            }
            StructuredLineKind::Del => {
                let removal = new_cur;
                let old_n = line.old.unwrap_or(old_cur);
                if deletion_selected(removal, intervals) {
                    out_lines.push(line.clone());
                    any_change = true;
                } else {
                    let text: String = line.segments.iter().map(|s| s.text.as_str()).collect();
                    out_lines.push(StructuredLine {
                        kind: StructuredLineKind::Context,
                        old: Some(old_n),
                        new: Some(removal),
                        segments: vec![StructuredSegment {
                            text,
                            emphasis: false,
                        }],
                        no_newline_at_eof: line.no_newline_at_eof,
                    });
                }
                old_cur = old_n.saturating_add(1);
            }
            StructuredLineKind::Add => {
                let new_n = line.new.unwrap_or(new_cur);
                if line_in_intervals(new_n, intervals) {
                    out_lines.push(line.clone());
                    any_change = true;
                }
                new_cur = new_n.saturating_add(1);
            }
        }
    }

    if !any_change {
        return None;
    }

    let mut filtered = StructuredHunk {
        old_start: hunk.old_start,
        new_start: hunk.new_start,
        old_lines: hunk.old_lines,
        new_lines: hunk.new_lines,
        context: hunk.context.clone(),
        lines: out_lines,
    };
    recount_structured_hunk(&mut filtered);
    Some(filtered)
}

fn recount_structured_hunk(hunk: &mut StructuredHunk) {
    let mut old_start = None;
    let mut new_start = None;
    let mut old_count = 0usize;
    let mut new_count = 0usize;
    let mut old_line = 0usize;
    let mut new_line = 0usize;

    for line in &mut hunk.lines {
        match line.kind {
            StructuredLineKind::Context => {
                if old_start.is_none() {
                    old_start = line.old.or(Some(old_line));
                    new_start = line.new.or(Some(new_line));
                }
                old_count += 1;
                new_count += 1;
                if let Some(o) = line.old {
                    old_line = o.saturating_add(1);
                } else {
                    old_line = old_line.saturating_add(1);
                }
                if let Some(n) = line.new {
                    new_line = n.saturating_add(1);
                } else {
                    new_line = new_line.saturating_add(1);
                }
            }
            StructuredLineKind::Del => {
                if old_start.is_none() {
                    old_start = line.old.or(Some(old_line));
                    new_start = Some(new_line);
                }
                old_count += 1;
                if let Some(o) = line.old {
                    old_line = o.saturating_add(1);
                } else {
                    old_line = old_line.saturating_add(1);
                }
            }
            StructuredLineKind::Add => {
                if old_start.is_none() {
                    old_start = Some(old_line);
                    new_start = line.new.or(Some(new_line));
                }
                new_count += 1;
                if let Some(n) = line.new {
                    new_line = n.saturating_add(1);
                } else {
                    new_line = new_line.saturating_add(1);
                }
            }
        }
    }

    hunk.old_start = old_start.unwrap_or(1);
    hunk.new_start = new_start.unwrap_or(1);
    hunk.old_lines = old_count;
    hunk.new_lines = new_count;
}

fn resolve_line_ranges_unstaged(
    changes: &[FileChange],
    peer_hunks: &HashMap<String, Vec<StructuredHunk>>,
    opts: &DiffOptions,
    selection: &HunkSelection,
    id_selected: &HashSet<HunkId>,
) -> std::result::Result<ResolvedSelection, HunkSelectError> {
    let mut by_path: BTreeMap<String, Vec<(usize, usize)>> = BTreeMap::new();
    let mut labels: BTreeMap<String, Vec<String>> = BTreeMap::new();
    for range in &selection.ranges {
        by_path
            .entry(range.path.clone())
            .or_default()
            .push((range.start, range.end));
        labels
            .entry(range.path.clone())
            .or_default()
            .push(range_label(range.start, range.end));
    }

    let mut patches = Vec::new();
    let mut staged_lines = BTreeMap::new();

    for (path, raw_intervals) in by_path {
        let intervals = merge_intervals(&raw_intervals);
        let change = changes
            .iter()
            .find(|c| c.path == path)
            .ok_or_else(|| HunkSelectError::RangeSelectsNothing { path: path.clone() })?;
        if change.binary {
            return Err(HunkSelectError::Binary { path: path.clone() });
        }
        let file = build_file_diff(change, opts);
        if !include_file_in_diff(&file, opts) {
            return Err(HunkSelectError::RangeSelectsNothing { path });
        }
        validate_line_ranges(&path, &intervals, new_side_line_count(change))?;
        let peer = peer_hunks.get(&path).map(|h| h.as_slice()).unwrap_or(&[]);
        let ids = hunk_ids_with_duplicate_peers(DiffSide::Unstaged, &path, &file.hunks, peer);
        let mut partial = Vec::new();
        let mut selected_any = false;
        for (hunk, id) in file.hunks.iter().zip(ids.iter()) {
            if id_selected.contains(id) {
                continue;
            }
            if let Some(filtered) = filter_hunk_by_intervals(hunk, &intervals) {
                selected_any = true;
                partial.push(filtered);
            }
        }
        let id_covered_any = file
            .hunks
            .iter()
            .zip(ids.iter())
            .any(|(_, id)| id_selected.contains(id));
        if !selected_any && !id_covered_any {
            return Err(HunkSelectError::RangeSelectsNothing { path: path.clone() });
        }
        if selected_any {
            patches.push(file_patch_from_hunks(&file, &partial)?);
        }
        if let Some(labs) = labels.remove(&path) {
            staged_lines.insert(path, labs);
        }
    }

    Ok(ResolvedSelection {
        patches,
        selected_hunks: BTreeMap::new(),
        selected_lines: staged_lines,
        whole_files: BTreeSet::new(),
    })
}

fn structured_hunk_to_apply_hunk(hunk: &StructuredHunk, first_body_line: usize) -> Hunk {
    let mut lines = Vec::new();
    for line in &hunk.lines {
        let text: String = line.segments.iter().map(|s| s.text.as_str()).collect();
        match line.kind {
            StructuredLineKind::Context => lines.push(HunkLine::Context(text)),
            StructuredLineKind::Add => lines.push(HunkLine::Add(text)),
            StructuredLineKind::Del => lines.push(HunkLine::Remove(text)),
        }
        if line.no_newline_at_eof {
            lines.push(HunkLine::NoNewline);
        }
    }
    Hunk {
        old_start: hunk.old_start,
        old_count: hunk.old_lines,
        new_start: hunk.new_start,
        new_count: hunk.new_lines,
        first_body_line,
        lines,
    }
}

/// Outcome of [`restore_hunks`].
#[derive(Debug, Clone, PartialEq, Eq, Default)]
pub struct RestoreHunksOutcome {
    /// Whether this was a dry run.
    pub dry_run: bool,
    /// Paths whose working tree or index was updated.
    pub restored: Vec<String>,
    /// Hunk ids restored per path (repository-relative).
    pub restored_hunks: BTreeMap<String, Vec<HunkId>>,
    /// Line ranges restored per path (`start` or `start-end` strings).
    pub restored_lines: BTreeMap<String, Vec<String>>,
    /// Paths removed (reserved; empty for partial hunk restore).
    pub removed: Vec<String>,
}

/// Discard or unstage the hunks in `selection`.
///
/// With `restore_worktree` (default when `restore_staged` is false), reverse-applies unstaged
/// hunks onto the worktree using clean diff bytes and checkout smudge rules. Unless `dry_run`,
/// this holds the index lock throughout but writes the index only when the stat refresh of a
/// restored path changes its entry (for example once the file matches the index again). With
/// `restore_staged`, reverse-applies staged hunks onto the index. Validates every patch before
/// writing anything.
///
/// # Errors
///
/// [`HunkSelectError`] for resolution failures; [`ApplyError`] for apply failures.
pub fn restore_hunks(
    repo: &Repository,
    selection: &HunkSelection,
    pathspecs: &[String],
    restore_staged: bool,
    restore_worktree: bool,
    dry_run: bool,
) -> std::result::Result<RestoreHunksOutcome, HunkSelectError> {
    let diff_opts = diff_options_for_hunk_select(repo)?;
    let restore_worktree = restore_worktree || !restore_staged;
    let mut outcome = RestoreHunksOutcome {
        dry_run,
        ..RestoreHunksOutcome::default()
    };
    if restore_staged {
        let side = DiffSide::Staged;
        let resolved =
            resolve_selection_with_staged(repo, side, selection, pathspecs, diff_opts.clone())?;
        let apply = apply_patch_to_index_and_write(
            repo,
            &resolved.patches,
            &IndexApplyOptions {
                dry_run,
                reverse: true,
                head_tree_oid: repo.head_tree()?,
            },
            &crate::progress::NeverCancel,
        )?;
        outcome
            .restored
            .extend(apply.added.into_iter().chain(apply.modified));
        outcome.restored.sort();
        outcome.restored.dedup();
        outcome.restored_hunks = resolved.selected_hunks;
        outcome.restored_lines = resolved.selected_lines;
    }
    if restore_worktree {
        // One index read serves the diff, the plan and the stat refresh; taking the lock first
        // keeps that read current for the (rare) refresh that has to be written.
        let handle = repo.index_handle();
        let lock = if dry_run {
            None
        } else {
            Some(handle.begin_update()?)
        };
        let mut index = handle.load()?;
        let resolved = resolve_selection_in(
            repo,
            Some(&mut index),
            DiffSide::Unstaged,
            selection,
            pathspecs,
            diff_opts,
        )?;
        let rules = WorktreeRules::from_repository(repo, &index).map_err(HunkSelectError::from)?;
        let planned = plan_worktree_reverse(
            repo,
            &index,
            &rules,
            &resolved.patches,
            &resolved.whole_files,
        )?;
        match lock {
            Some(lock) => {
                commit_worktree_reverse(repo, lock, index, &rules, &planned, &mut outcome)?
            }
            None => {
                for plan in &planned {
                    push_restored_path(&mut outcome.restored, &plan.path);
                }
            }
        }
        merge_restored_maps(&mut outcome.restored_hunks, resolved.selected_hunks);
        merge_restored_line_maps(&mut outcome.restored_lines, resolved.selected_lines);
    }
    Ok(outcome)
}

fn merge_restored_maps(
    into: &mut BTreeMap<String, Vec<HunkId>>,
    other: BTreeMap<String, Vec<HunkId>>,
) {
    for (path, ids) in other {
        into.entry(path).or_default().extend(ids);
    }
}

fn merge_restored_line_maps(
    into: &mut BTreeMap<String, Vec<String>>,
    other: BTreeMap<String, Vec<String>>,
) {
    for (path, ranges) in other {
        into.entry(path).or_default().extend(ranges);
    }
}

fn push_restored_path(restored: &mut Vec<String>, path: &str) {
    if !restored.iter().any(|p| p == path) {
        restored.push(path.to_string());
    }
}

struct WorktreeReversePlan {
    path: String,
    clean_bytes: Vec<u8>,
    mode: u32,
    /// Whether the restored file can match its index entry again, which is the only case where
    /// refreshing the entry's stat data changes anything. A file that keeps some unstaged hunk
    /// stays different from the index, and leaving its stat data alone is what `git apply` does.
    may_match_index: bool,
}

/// Reverse-apply each patch to the clean worktree content of its path.
///
/// `whole_files` lists the paths whose every unstaged hunk is in `patches`
/// ([`ResolvedSelection::whole_files`]).
fn plan_worktree_reverse(
    repo: &Repository,
    index: &Index,
    rules: &WorktreeRules,
    patches: &[FilePatch],
    whole_files: &BTreeSet<String>,
) -> std::result::Result<Vec<WorktreeReversePlan>, HunkSelectError> {
    let work_tree = repo.work_tree().ok_or(Error::RequiresWorkTree)?;
    let config = repo.config().map_err(HunkSelectError::from)?;
    let mut out = Vec::with_capacity(patches.len());
    for patch in patches {
        let path = patch
            .effective_path()
            .ok_or(HunkSelectError::MissingPath)?
            .to_string();
        if patch.involves_gitlink() {
            return Err(HunkSelectError::Gitlink { path });
        }
        let entry = index.get(path.as_bytes(), 0);
        let mode = entry.map(|e| e.mode).unwrap_or(MODE_REGULAR);
        if mode != MODE_REGULAR && mode != MODE_EXECUTABLE {
            return Err(HunkSelectError::Binary { path: path.clone() });
        }
        let abs = crate::repo_relpath::worktree_abs(work_tree, &path);
        let clean = if patch.is_deleted || !abs.exists() {
            Vec::new()
        } else {
            read_worktree_side_bytes_for_diff(
                repo.odb(),
                work_tree,
                &path,
                mode,
                config.as_ref(),
                entry,
                Some(rules),
            )
            .map_err(HunkSelectError::from)?
        };
        let new_clean = apply_hunks_to_blob(&clean, &patch.hunks, &ApplyOptions { reverse: true })
            .map_err(HunkSelectError::Apply)?;
        let may_match_index = whole_files.contains(&path);
        out.push(WorktreeReversePlan {
            path,
            clean_bytes: new_clean,
            mode,
            may_match_index,
        });
    }
    Ok(out)
}

/// Write the planned worktree files, then refresh their index stat data.
///
/// `index` must have been loaded while holding `lock`, and `rules` built from it. It is only
/// written when the refresh changed an entry (a restore that leaves the file different from the
/// index changes nothing, as with `git apply`); otherwise the lock is released untouched.
fn commit_worktree_reverse(
    repo: &Repository,
    mut lock: IndexLock,
    mut index: Index,
    rules: &WorktreeRules,
    planned: &[WorktreeReversePlan],
    outcome: &mut RestoreHunksOutcome,
) -> std::result::Result<(), HunkSelectError> {
    let work_tree = repo.work_tree().ok_or(Error::RequiresWorkTree)?;
    let config = repo.config().map_err(HunkSelectError::from)?;
    let mut dir_cache = LeadingDirCache::for_config(config.as_ref());
    let has_symlinks = dir_cache.has_symlinks();
    for plan in planned {
        let attrs = rules.file_attrs(&plan.path, false);
        let smudged;
        let worktree_bytes = if worktree_conversion_is_identity(rules.conversion(), &attrs) {
            plan.clean_bytes.as_slice()
        } else {
            // The restored content only lives in the worktree, so it is hashed (for `ident` and
            // filter metadata) but not stored.
            let oid = repo
                .odb()
                .hash_algo()
                .hash_object(ObjectKind::Blob, &plan.clean_bytes)
                .map_err(HunkSelectError::from)?;
            smudged = smudge_bytes_for_worktree_path(
                repo,
                rules,
                &plan.path,
                plan.mode,
                &plan.clean_bytes,
                &oid,
            )
            .map_err(HunkSelectError::from)?;
            smudged.as_slice()
        };
        write_to_worktree_cached(
            work_tree,
            &plan.path,
            worktree_bytes,
            plan.mode,
            &mut dir_cache,
            has_symlinks,
        )?;
        push_restored_path(&mut outcome.restored, &plan.path);
    }
    let still_different: BTreeSet<&str> = planned
        .iter()
        .filter(|plan| !plan.may_match_index)
        .map(|plan| plan.path.as_str())
        .collect();
    let touched: BTreeSet<&str> = outcome
        .restored
        .iter()
        .map(String::as_str)
        .filter(|path| !still_different.contains(path))
        .collect();
    if refresh_stage0_index_stats_for_paths(repo, work_tree, &mut index, &touched)? {
        repo.index_handle()
            .commit_update(&mut lock, &mut index, false)?;
    }
    Ok(())
}

/// Options for [`reverse_apply_patches_to_worktree`].
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct WorktreeReverseApplyOptions {
    /// When true, validate patches without writing the worktree or new blobs.
    pub dry_run: bool,
}

/// Reverse-apply unstaged [`FilePatch`] rows onto the worktree (undo selected local edits).
///
/// Used after partial `stash push` so only the stashed hunks disappear from disk while the
/// index and other unstaged edits stay put. Reports
/// [`crate::progress::ProgressPhase::CheckingOutFiles`], one unit per patch, and polls `cancel`
/// before each file; files already rewritten stay rewritten.
///
/// # Errors
///
/// [`ApplyError`] when a patch cannot be reversed on the worktree, and
/// [`ApplyError::Cancelled`] when `cancel` or [`ProgressSink::should_cancel`] fired.
pub fn reverse_apply_patches_to_worktree(
    repo: &Repository,
    patches: &[FilePatch],
    opts: &WorktreeReverseApplyOptions,
    progress: &mut dyn ProgressSink,
    cancel: &dyn Cancel,
) -> std::result::Result<(), ApplyError> {
    let work_tree = repo.work_tree().ok_or_else(|| ApplyError::Failed {
        path: String::new(),
        message: "worktree reverse apply requires a working tree".into(),
    })?;
    let index = repo.load_index().map_err(|e| ApplyError::Failed {
        path: String::new(),
        message: e.to_string(),
    })?;
    let config = repo.config().map_err(|e| ApplyError::Failed {
        path: String::new(),
        message: e.to_string(),
    })?;
    let rules = WorktreeRules::from_repository(repo, &index).map_err(|e| ApplyError::Failed {
        path: String::new(),
        message: e.to_string(),
    })?;
    progress.start(ProgressPhase::CheckingOutFiles, Some(patches.len() as u64));
    for patch in patches {
        poll_cancel(progress, cancel).map_err(|_| ApplyError::Cancelled)?;
        progress.inc(1);
        if patch.involves_gitlink() {
            let path = patch.effective_path().unwrap_or("<unknown>").to_string();
            return Err(ApplyError::Failed {
                path,
                message: "submodule/gitlink patches are not supported".into(),
            });
        }
        let path = patch
            .target_path()
            .map(str::to_string)
            .or_else(|| patch.effective_path().map(str::to_string))
            .ok_or_else(|| ApplyError::Failed {
                path: String::new(),
                message: "patch has no target path".into(),
            })?;

        if patch.is_deleted {
            let Some(entry) = index.get(path.as_bytes(), 0) else {
                return Err(ApplyError::NotInIndex { path: path.clone() });
            };
            if entry.mode == MODE_GITLINK {
                continue;
            }
            if !opts.dry_run {
                write_smudged_blob_to_worktree(
                    repo, work_tree, &rules, &path, &entry.oid, entry.mode,
                )
                .map_err(|e| ApplyError::Failed {
                    path: path.clone(),
                    message: e.to_string(),
                })?;
            }
            continue;
        }

        if patch.is_new {
            if !opts.dry_run {
                let abs = crate::repo_relpath::worktree_abs(work_tree, &path);
                if let Ok(meta) = fs::symlink_metadata(&abs) {
                    if meta.is_dir() {
                        let _ = fs::remove_dir_all(&abs);
                    } else {
                        fs::remove_file(&abs).map_err(|e| ApplyError::Failed {
                            path: path.clone(),
                            message: e.to_string(),
                        })?;
                    }
                    remove_empty_parent_dirs(work_tree, &abs);
                }
            }
            continue;
        }

        let mode = index
            .get(path.as_bytes(), 0)
            .map(|e| e.mode)
            .unwrap_or(MODE_REGULAR);
        if mode == MODE_GITLINK {
            continue;
        }
        let index_entry = index.get(path.as_bytes(), 0);
        let base = read_worktree_side_bytes_for_diff(
            repo.odb(),
            work_tree,
            &path,
            mode,
            config.as_ref(),
            index_entry,
            Some(&rules),
        )
        .map_err(|e| ApplyError::Failed {
            path: path.clone(),
            message: e.to_string(),
        })?;
        let new_clean = apply_hunks_to_blob(&base, &patch.hunks, &ApplyOptions { reverse: true })?;
        if opts.dry_run {
            continue;
        }
        let oid = repo
            .odb()
            .write(ObjectKind::Blob, &new_clean)
            .map_err(|e| ApplyError::Failed {
                path: path.clone(),
                message: e.to_string(),
            })?;
        write_smudged_blob_to_worktree(repo, work_tree, &rules, &path, &oid, mode).map_err(
            |e| ApplyError::Failed {
                path: path.clone(),
                message: e.to_string(),
            },
        )?;
    }
    progress.finish();
    Ok(())
}

/// Diff options for hunk id resolution (same hunk boundaries as `grit diff --json`).
///
/// # Errors
///
/// Returns repository config errors.
pub fn diff_options_for_hunk_select(repo: &Repository) -> std::result::Result<DiffOptions, Error> {
    let config = repo.config()?;
    Ok(DiffOptions::from_config(config.as_ref()))
}

/// Stage the hunks in `selection` on `side` (typically unstaged for `grit add --hunks`).
///
/// `diff_options` must match the options used when the hunk ids were produced (`grit diff --json`,
/// including `-U` / config `diff.context`).
///
/// # Errors
///
/// [`HunkSelectError`] for resolution failures; [`ApplyError`] for index apply failures.
pub fn stage_hunks(
    repo: &Repository,
    side: DiffSide,
    selection: &HunkSelection,
    pathspecs: &[String],
    diff_options: DiffOptions,
    dry_run: bool,
    cancel: &dyn crate::progress::Cancel,
) -> std::result::Result<StageHunksOutcome, HunkSelectError> {
    // Lock first so the selection is resolved against the index the patches are applied to. The
    // index is reloaded rather than kept across the diff, which would add it to the diff's peak.
    let handle = repo.index_handle();
    let mut lock = if dry_run {
        None
    } else {
        Some(handle.begin_update()?)
    };
    crate::progress::poll_cancel(&mut crate::progress::NullProgress, cancel)
        .map_err(|_| HunkSelectError::Cancelled)?;
    let resolved = resolve_selection_in(repo, None, side, selection, pathspecs, diff_options)?;
    crate::progress::poll_cancel(&mut crate::progress::NullProgress, cancel)
        .map_err(|_| HunkSelectError::Cancelled)?;
    let mut index = handle.load()?;
    let apply = apply_patch_to_index(
        repo,
        &mut index,
        &resolved.patches,
        &IndexApplyOptions {
            dry_run,
            ..IndexApplyOptions::default()
        },
    )?;
    crate::progress::poll_cancel(&mut crate::progress::NullProgress, cancel)
        .map_err(|_| HunkSelectError::Cancelled)?;
    if let Some(lock) = lock.as_mut() {
        handle.commit_update(lock, &mut index, false)?;
    }
    Ok(StageHunksOutcome::from_apply(
        dry_run,
        resolved.selected_hunks,
        resolved.selected_lines,
        apply,
    ))
}

fn map_parse_err(_err: Error) -> HunkSelectError {
    HunkSelectError::PatchBuild
}

/// Unstaged hunk ids per path (same assignment rules as `grit diff --json` on `--unstaged`).
///
/// # Errors
///
/// Propagates repository and diff errors.
pub fn list_unstaged_hunk_ids(
    repo: &Repository,
    pathspecs: &[String],
    diff_options: DiffOptions,
) -> std::result::Result<BTreeMap<String, Vec<HunkId>>, Error> {
    let (changes, peer_hunks) =
        unstaged_raw_changes_with_peer_hunks(repo, pathspecs, diff_options.clone())?;
    let mut out = BTreeMap::new();
    for change in &changes {
        if change.binary {
            continue;
        }
        let peer = peer_hunks
            .get(&change.path)
            .map(|h| h.as_slice())
            .unwrap_or(&[]);
        let old_text = side_text(&change.old_bytes);
        let new_text = side_text(&change.new_bytes);
        let body =
            unified_hunk_body_for_diff_options(old_text.as_ref(), new_text.as_ref(), &diff_options);
        let slices = imara_unified_hunk_slices(&body);
        let ids = crate::diff::hunk_id::hunk_ids_for_unified_slices(
            DiffSide::Unstaged,
            &change.path,
            &slices,
            line_count(old_text.as_ref()),
            line_count(new_text.as_ref()),
            old_text.as_ref().ends_with('\n'),
            new_text.as_ref().ends_with('\n'),
            peer,
        );
        out.insert(change.path.clone(), ids);
    }
    Ok(out)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::diff::hunk_diff_bundle;
    use crate::diff::hunk_id::hunk_ids;
    use crate::index::write_tree::write_tree_from_index;
    use crate::porcelain::add::{stage, StageOptions};
    use crate::progress::NullProgress;
    use crate::repo::{InitOptions, Repository};
    use std::process::Command;

    fn git(dir: &std::path::Path, args: &[&str]) {
        let out = Command::new("git")
            .current_dir(dir)
            .args(args)
            .env("GIT_CONFIG_GLOBAL", "/dev/null")
            .env("GIT_CONFIG_SYSTEM", "/dev/null")
            .output()
            .expect("git");
        assert!(
            out.status.success(),
            "git {args:?}: {}",
            String::from_utf8_lossy(&out.stderr)
        );
    }

    fn hunk_diff_opts() -> DiffOptions {
        DiffOptions::default()
    }

    fn init_repo() -> (tempfile::TempDir, Repository) {
        let dir = tempfile::tempdir().expect("tempdir");
        git(dir.path(), &["init", "-q", "-b", "main"]);
        let repo = Repository::init(dir.path(), &InitOptions::default()).expect("init");
        (dir, repo)
    }

    fn spaced_two_hunk_body() -> (String, String) {
        three_hunk_body()
    }

    fn three_hunk_body() -> (String, String) {
        let mut base = String::new();
        for i in 0..30 {
            base.push_str(&format!("line{i}\n"));
        }
        let mut edited = base.clone();
        edited = edited.replacen("line5\n", "LINE5\n", 1);
        edited = edited.replacen("line13\n", "LINE13\n", 1);
        edited = edited.replacen("line21\n", "LINE21\n", 1);
        (base, edited)
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_subset_matches_git_apply_cached() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let (base, edited) = spaced_two_hunk_body();
        std::fs::write(root.join("f.txt"), base).unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);

        std::fs::write(root.join("f.txt"), edited).unwrap();
        let (files, peers) =
            unstaged_file_diffs_with_peer_hunks(&repo, &[], DiffOptions::default()).unwrap();
        assert_eq!(files.len(), 1);
        let ids = hunk_ids_with_duplicate_peers(
            DiffSide::Unstaged,
            "f.txt",
            &files[0].hunks,
            peers.get("f.txt").map(|v| v.as_slice()).unwrap_or(&[]),
        );
        assert!(ids.len() >= 2);
        let selection = HunkSelection {
            ids: vec![ids[0].clone()],
            ranges: Vec::new(),
        };

        let patch = resolve_selection(&repo, DiffSide::Unstaged, &selection, &[], hunk_diff_opts())
            .unwrap();
        let mut patch_text = String::new();
        for p in &patch {
            patch_text.push_str(&format_patch_for_git(p));
        }

        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        let grit_tree =
            write_tree_from_index(repo.odb(), &repo.index_handle().load().unwrap(), "").unwrap();

        git(root, &["read-tree", "HEAD"]);
        let patch_path = root.join("partial.diff");
        std::fs::write(&patch_path, patch_text).unwrap();
        git(root, &["apply", "--cached", patch_path.to_str().unwrap()]);
        let git_tree = Command::new("git")
            .current_dir(root)
            .args(["write-tree"])
            .output()
            .expect("write-tree");
        let git_tree_hex = String::from_utf8_lossy(&git_tree.stdout).trim().to_string();
        assert_eq!(grit_tree.to_hex(), git_tree_hex);
        git(root, &["fsck"]);
    }

    fn write_hunk_line(out: &mut String, prefix: char, text: &str) {
        out.push(prefix);
        if text.ends_with('\n') {
            out.push_str(text);
        } else {
            out.push_str(text);
            out.push('\n');
        }
    }

    fn format_patch_for_git(patch: &FilePatch) -> String {
        let mut out = String::new();
        let path = patch.effective_path().unwrap_or("f");
        out.push_str(&format!("diff --git a/{path} b/{path}\n"));
        if patch.is_new {
            out.push_str("new file mode 100644\n");
        }
        let old = if patch.is_new {
            "/dev/null".to_string()
        } else {
            format!("a/{}", patch.old_path.as_deref().unwrap_or(path))
        };
        let new = if patch.is_deleted {
            "/dev/null".to_string()
        } else {
            format!("b/{}", patch.new_path.as_deref().unwrap_or(path))
        };
        out.push_str(&format!("--- {old}\n"));
        out.push_str(&format!("+++ {new}\n"));
        for h in &patch.hunks {
            out.push_str(&format!(
                "@@ -{},{} +{},{} @@\n",
                h.old_start, h.old_count, h.new_start, h.new_count
            ));
            for line in &h.lines {
                match line {
                    HunkLine::Context(s) => write_hunk_line(&mut out, ' ', s),
                    HunkLine::Add(s) => write_hunk_line(&mut out, '+', s),
                    HunkLine::Remove(s) => write_hunk_line(&mut out, '-', s),
                    HunkLine::NoNewline => out.push_str("\\ No newline at end of file\n"),
                }
            }
        }
        out
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_sequential_ids_stay_valid() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let (base, edited) = spaced_two_hunk_body();
        std::fs::write(root.join("f.txt"), base).unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), edited).unwrap();

        let (files, peers) =
            unstaged_file_diffs_with_peer_hunks(&repo, &[], DiffOptions::default()).unwrap();
        let ids = hunk_ids_with_duplicate_peers(
            DiffSide::Unstaged,
            "f.txt",
            &files[0].hunks,
            peers.get("f.txt").map(|v| v.as_slice()).unwrap_or(&[]),
        );
        assert_eq!(ids.len(), 3, "expected three hunks, got {}", ids.len());
        let id0 = ids[0].clone();
        let id2 = ids[2].clone();
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: vec![id0],
                ranges: Vec::new(),
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: vec![id2],
                ranges: Vec::new(),
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        git(root, &["fsck"]);
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_inter_hunk_context_matches_diff_ids() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        git(root, &["config", "diff.interHunkContext", "1"]);
        let (base, _edited) = three_hunk_body();
        let mut edited_two = base.clone();
        edited_two = edited_two.replacen("line5\n", "LINE5\n", 1);
        edited_two = edited_two.replacen("line13\n", "LINE13\n", 1);
        std::fs::write(root.join("f.txt"), base).unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), edited_two).unwrap();

        let opts = DiffOptions::from_config(repo.config().unwrap().as_ref());
        let (files, peers) = unstaged_file_diffs_with_peer_hunks(&repo, &[], opts.clone()).unwrap();
        let ids = hunk_ids_with_duplicate_peers(
            DiffSide::Unstaged,
            "f.txt",
            &files[0].hunks,
            peers.get("f.txt").map(|v| v.as_slice()).unwrap_or(&[]),
        );
        assert_eq!(
            ids.len(),
            1,
            "interHunkContext=1 should merge edits at lines 5 and 13"
        );
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: vec![ids[0].clone()],
                ranges: Vec::new(),
            },
            &[],
            opts,
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        git(root, &["fsck"]);
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_text_to_binary_returns_binary_error() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let (base, edited) = spaced_two_hunk_body();
        std::fs::write(root.join("f.txt"), base).unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), edited).unwrap();
        let (files, peers) =
            unstaged_file_diffs_with_peer_hunks(&repo, &[], DiffOptions::default()).unwrap();
        let ids = hunk_ids_with_duplicate_peers(
            DiffSide::Unstaged,
            "f.txt",
            &files[0].hunks,
            peers.get("f.txt").map(|v| v.as_slice()).unwrap_or(&[]),
        );
        let id = ids[0].clone();
        let binary = b"before\0after".to_vec();
        std::fs::write(root.join("f.txt"), &binary).unwrap();
        let err = stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: vec![id],
                ranges: Vec::new(),
            },
            &["f.txt".into()],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap_err();
        assert!(
            matches!(err, HunkSelectError::Binary { .. }),
            "expected Binary, got {err:?}"
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_stale_id_rejected_index_untouched() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"one\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"two\n").unwrap();
        let before = repo.index_handle().load().unwrap();
        let stale = HunkId::from_str("000000000001").unwrap();
        let err = stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: vec![stale.clone()],
                ranges: Vec::new(),
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap_err();
        assert!(matches!(err, HunkSelectError::StaleId { .. }));
        let after = repo.index_handle().load().unwrap();
        assert_eq!(before.entries.len(), after.entries.len());
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_staged_side_id_rejected() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"one\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"two\n").unwrap();
        stage(
            &repo,
            &StageOptions::default(),
            &mut NullProgress,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        let staged_files =
            collect_files_for_target(&repo, &DiffTarget::IndexVsHead, &[], DiffOptions::default())
                .unwrap();
        let staged_id = hunk_ids(DiffSide::Staged, "f.txt", &staged_files[0].hunks)[0].clone();
        std::fs::write(root.join("f.txt"), b"three\n").unwrap();
        let err = stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: vec![staged_id],
                ranges: Vec::new(),
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap_err();
        assert!(matches!(
            err,
            HunkSelectError::WrongSide {
                actual_side: DiffSide::Staged,
                requested_side: DiffSide::Unstaged,
                ..
            }
        ));
    }

    #[test]
    fn wrong_side_message_names_both_sides() {
        let err = HunkSelectError::WrongSide {
            id: HunkId::from_bytes([0xab; 6]),
            actual_side: DiffSide::Staged,
            requested_side: DiffSide::Unstaged,
        };
        assert_eq!(
            err.to_string(),
            "hunk id abababababab is for the staged side, not unstaged"
        );
    }

    #[test]
    fn repository_error_keeps_typed_source() {
        let err = HunkSelectError::from(Error::InvalidHead);
        assert_eq!(err.to_string(), Error::InvalidHead.to_string());
        match err {
            HunkSelectError::Repository(inner) => assert!(matches!(*inner, Error::InvalidHead)),
            other => panic!("expected Repository, got {other:?}"),
        }
    }

    #[test]
    fn other_side_is_unselectable() {
        let dir = tempfile::tempdir().unwrap();
        let repo = Repository::init(dir.path(), &InitOptions::default()).unwrap();
        let by_id = HunkSelection {
            ids: vec![HunkId::from_bytes([1; 6])],
            ranges: Vec::new(),
        };
        let by_range = HunkSelection {
            ids: Vec::new(),
            ranges: vec![LineRange {
                path: "f.txt".into(),
                start: 1,
                end: 1,
            }],
        };
        for selection in [by_id, by_range] {
            let err = resolve_selection(&repo, DiffSide::Other, &selection, &[], hunk_diff_opts())
                .unwrap_err();
            assert!(
                matches!(
                    err,
                    HunkSelectError::UnselectableSide {
                        side: DiffSide::Other
                    }
                ),
                "{err:?}"
            );
        }
    }

    fn one_line_patch(path: &str) -> FilePatch {
        let text = format!(
            "diff --git a/{path} b/{path}\n--- a/{path}\n+++ b/{path}\n@@ -1 +1 @@\n-old\n+new\n"
        );
        parse_patch(&text, 1, path, false, None)
            .unwrap()
            .pop()
            .unwrap()
    }

    fn plan_without_selection(
        repo: &Repository,
        patches: &[FilePatch],
    ) -> std::result::Result<Vec<WorktreeReversePlan>, HunkSelectError> {
        let index = Index::new();
        let rules = WorktreeRules::from_repository(repo, &index)?;
        plan_worktree_reverse(repo, &index, &rules, patches, &BTreeSet::new())
    }

    #[test]
    fn restore_plan_requires_work_tree() {
        let dir = tempfile::tempdir().unwrap();
        let repo = Repository::init(
            dir.path(),
            &InitOptions {
                bare: true,
                ..InitOptions::default()
            },
        )
        .unwrap();
        let err = plan_without_selection(&repo, &[one_line_patch("f.txt")])
            .err()
            .unwrap();
        match err {
            HunkSelectError::Repository(inner) => {
                assert!(matches!(*inner, Error::RequiresWorkTree), "{inner:?}");
            }
            other => panic!("expected Repository(RequiresWorkTree), got {other:?}"),
        }
    }

    #[test]
    fn restore_plan_rejects_gitlink_and_pathless_patches() {
        let dir = tempfile::tempdir().unwrap();
        let repo = Repository::init(dir.path(), &InitOptions::default()).unwrap();

        let mut gitlink = one_line_patch("sub");
        gitlink.new_mode = Some("160000".into());
        let err = plan_without_selection(&repo, &[gitlink]).err().unwrap();
        assert!(
            matches!(&err, HunkSelectError::Gitlink { path } if path == "sub"),
            "{err:?}"
        );

        let mut pathless = one_line_patch("f.txt");
        pathless.old_path = None;
        pathless.new_path = None;
        let err = plan_without_selection(&repo, &[pathless]).err().unwrap();
        assert!(matches!(err, HunkSelectError::MissingPath), "{err:?}");
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_new_file_whole() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("base.txt"), b"keep\n").unwrap();
        git(root, &["add", "base.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("new.txt"), b"hello\n").unwrap();
        stage(
            &repo,
            &StageOptions {
                pathspecs: vec!["new.txt".into()],
                intent_to_add: true,
                ..StageOptions::default()
            },
            &mut NullProgress,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        let (files, peers) =
            unstaged_file_diffs_with_peer_hunks(&repo, &[], DiffOptions::default()).unwrap();
        let new_file = files
            .iter()
            .find(|f| f.path == "new.txt")
            .expect("new file in unstaged diff");
        assert!(
            !new_file.hunks.is_empty(),
            "new file should have structured hunks"
        );
        let ids = hunk_ids_with_duplicate_peers(
            DiffSide::Unstaged,
            "new.txt",
            &new_file.hunks,
            peers.get("new.txt").map(|v| v.as_slice()).unwrap_or(&[]),
        );
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: ids.clone(),
                ranges: Vec::new(),
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        assert!(repo
            .index_handle()
            .load()
            .unwrap()
            .get(b"new.txt", 0)
            .is_some());
        git(root, &["fsck"]);
    }

    fn stage_lines_and_compare_git(
        repo: &Repository,
        root: &std::path::Path,
        path: &str,
        ranges: Vec<LineRange>,
    ) {
        let selection = HunkSelection {
            ids: Vec::new(),
            ranges,
        };
        let patch = resolve_selection(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &[path.into()],
            hunk_diff_opts(),
        )
        .unwrap();
        let mut patch_text = String::new();
        for p in &patch {
            patch_text.push_str(&format_patch_for_git(p));
        }
        let index_path = root.join(".git/index");
        let index_before = std::fs::read(&index_path).unwrap();
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &[path.into()],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        let grit_tree =
            write_tree_from_index(repo.odb(), &repo.index_handle().load().unwrap(), "").unwrap();
        std::fs::write(&index_path, index_before).unwrap();
        let patch_path = root.join("partial.diff");
        std::fs::write(&patch_path, patch_text).unwrap();
        git(root, &["apply", "--cached", patch_path.to_str().unwrap()]);
        let git_tree = Command::new("git")
            .current_dir(root)
            .args(["write-tree"])
            .output()
            .expect("write-tree");
        let git_tree_hex = String::from_utf8_lossy(&git_tree.stdout).trim().to_string();
        assert_eq!(grit_tree.to_hex(), git_tree_hex);
        git(root, &["fsck"]);
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn stage_hunks_whole_file_deletion_removes_index_entry() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("gone.txt"), b"keep\n").unwrap();
        git(root, &["add", "gone.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::remove_file(root.join("gone.txt")).unwrap();
        let ids = list_unstaged_hunk_ids(&repo, &[], hunk_diff_opts())
            .unwrap()
            .remove("gone.txt")
            .expect("deletion in unstaged diff");
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids,
                ranges: Vec::new(),
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        assert!(
            repo.index_handle()
                .load()
                .unwrap()
                .get(b"gone.txt", 0)
                .is_none(),
            "index entry removed after staging delete hunk"
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn directory_pathspec_keeps_staged_peer_hunk_ids() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::create_dir_all(root.join("pkg")).unwrap();
        let (base, edited) = spaced_two_hunk_body();
        std::fs::write(root.join("pkg/a.txt"), &base).unwrap();
        git(root, &["add", "pkg/a.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("pkg/a.txt"), &edited).unwrap();
        let (files, peers) =
            unstaged_file_diffs_with_peer_hunks(&repo, &[], DiffOptions::default()).unwrap();
        let file = files.iter().find(|f| f.path == "pkg/a.txt").expect("a.txt");
        let ids = hunk_ids_with_duplicate_peers(
            DiffSide::Unstaged,
            "pkg/a.txt",
            &file.hunks,
            peers.get("pkg/a.txt").map(|v| v.as_slice()).unwrap_or(&[]),
        );
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: vec![ids[0].clone()],
                ranges: Vec::new(),
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        let file_pathspec = vec!["pkg/a.txt".to_string()];
        let dir_pathspec = vec!["pkg/".to_string()];
        let opts = hunk_diff_opts();
        let by_file = list_unstaged_hunk_ids(&repo, &file_pathspec, opts.clone()).unwrap();
        let by_dir = list_unstaged_hunk_ids(&repo, &dir_pathspec, opts).unwrap();
        assert_eq!(
            by_file.get("pkg/a.txt"),
            by_dir.get("pkg/a.txt"),
            "directory pathspec must include staged peer hunks when assigning ids"
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_selects_part_of_hunk() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"a\nb\nc\nd\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"a\nB\nc\nD\n").unwrap();
        stage_lines_and_compare_git(
            &repo,
            root,
            "f.txt",
            vec![LineRange {
                path: "f.txt".into(),
                start: 2,
                end: 2,
            }],
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_unselected_deletion_becomes_context() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"keep\nremove\nstay\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"keep\nstay\n").unwrap();
        stage_lines_and_compare_git(
            &repo,
            root,
            "f.txt",
            vec![LineRange {
                path: "f.txt".into(),
                start: 1,
                end: 1,
            }],
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_selected_deletion_at_range_edge() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"a\nb\nc\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"a\nc\n").unwrap();
        stage_lines_and_compare_git(
            &repo,
            root,
            "f.txt",
            vec![LineRange {
                path: "f.txt".into(),
                start: 1,
                end: 1,
            }],
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_range_spanning_two_hunks() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let (base, edited) = three_hunk_body();
        std::fs::write(root.join("f.txt"), base).unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), edited).unwrap();
        stage_lines_and_compare_git(
            &repo,
            root,
            "f.txt",
            vec![LineRange {
                path: "f.txt".into(),
                start: 5,
                end: 14,
            }],
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn glob_pathspec_includes_file_in_hunk_bundle() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"a\nb\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"a\nB\n").unwrap();
        let bundle = hunk_diff_bundle(&repo, &[":(glob)*.txt".into()], DiffOptions::default())
            .expect("bundle");
        assert!(
            bundle.unstaged.iter().any(|f| f.path == "f.txt"),
            "expected f.txt in bundle, got {:?}",
            bundle
                .unstaged
                .iter()
                .map(|f| f.path.as_str())
                .collect::<Vec<_>>()
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_pathspec_glob_stages() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"a\nb\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"a\nB\n").unwrap();
        let selection = HunkSelection {
            ids: Vec::new(),
            ranges: vec![LineRange {
                path: "f.txt".into(),
                start: 2,
                end: 2,
            }],
        };
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &[":(glob)*.txt".into()],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        git(root, &["fsck"]);
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_mix_hunk_id_overlap_stages_via_id() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"one\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"two\n").unwrap();
        let (files, peers) =
            unstaged_file_diffs_with_peer_hunks(&repo, &[], DiffOptions::default()).unwrap();
        let ids = hunk_ids_with_duplicate_peers(
            DiffSide::Unstaged,
            "f.txt",
            &files[0].hunks,
            peers.get("f.txt").map(|v| v.as_slice()).unwrap_or(&[]),
        );
        let selection = HunkSelection {
            ids: vec![ids[0].clone()],
            ranges: vec![LineRange {
                path: "f.txt".into(),
                start: 1,
                end: 1,
            }],
        };
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &["f.txt".into()],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        git(root, &["fsck"]);
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_unchanged_line_beyond_hunk_is_selects_nothing() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let mut base = String::new();
        for i in 1..=100 {
            base.push_str(&format!("line{i}\n"));
        }
        std::fs::write(root.join("f.txt"), &base).unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        let mut edited = base.clone();
        edited = edited.replacen("line1\n", "LINE1\n", 1);
        std::fs::write(root.join("f.txt"), edited).unwrap();
        let err = stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: Vec::new(),
                ranges: vec![LineRange {
                    path: "f.txt".into(),
                    start: 100,
                    end: 100,
                }],
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap_err();
        assert!(
            matches!(err, HunkSelectError::RangeSelectsNothing { .. }),
            "expected RangeSelectsNothing, got {err:?}"
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_out_of_bounds_error() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"one\n").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"two\n").unwrap();
        let err = stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: Vec::new(),
                ranges: vec![LineRange {
                    path: "f.txt".into(),
                    start: 1,
                    end: 99,
                }],
            },
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap_err();
        assert!(matches!(err, HunkSelectError::RangeOutOfBounds { .. }));
    }

    #[cfg(unix)]
    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_symlink_dangling_target_matches_git_apply_cached() {
        use std::os::unix::fs::symlink;

        let (dir, repo) = init_repo();
        let root = dir.path();
        symlink("old-target", root.join("link")).expect("symlink");
        git(root, &["add", "link"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::remove_file(root.join("link")).expect("remove link");
        symlink("new-target", root.join("link")).expect("retarget");
        stage_lines_and_compare_git(
            &repo,
            root,
            "link",
            vec![LineRange {
                path: "link".into(),
                start: 1,
                end: 1,
            }],
        );
    }

    fn numbered_lines(n: usize) -> String {
        (1..=n).map(|i| format!("line{i}\n")).collect()
    }

    fn edit_every_tenth_line(base: &str) -> String {
        base.lines()
            .enumerate()
            .map(|(i, l)| {
                if i % 10 == 0 {
                    format!("{}\n", l.to_uppercase())
                } else {
                    format!("{l}\n")
                }
            })
            .collect()
    }

    #[test]
    fn stage_lines_dry_run_writes_nothing_and_stages_only_the_range() {
        let dir = tempfile::tempdir().unwrap();
        let root = dir.path();
        let repo = Repository::init(root, &InitOptions::default()).unwrap();
        let base = numbered_lines(40);
        std::fs::write(root.join("f.txt"), &base).unwrap();
        std::fs::write(root.join("other.txt"), b"other\n").unwrap();
        stage(
            &repo,
            &StageOptions::default(),
            &mut NullProgress,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        std::fs::write(root.join("f.txt"), edit_every_tenth_line(&base)).unwrap();
        std::fs::write(root.join("other.txt"), b"changed\n").unwrap();
        let selection = HunkSelection {
            ids: Vec::new(),
            ranges: vec![LineRange {
                path: "f.txt".into(),
                start: 1,
                end: 15,
            }],
        };
        let index_path = root.join(".git/index");
        let before = std::fs::read(&index_path).unwrap();
        let outcome = stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &["f.txt".into()],
            hunk_diff_opts(),
            true,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        assert!(outcome.dry_run);
        assert_eq!(outcome.modified, ["f.txt"]);
        assert_eq!(std::fs::read(&index_path).unwrap(), before);
        assert!(!root.join(".git/index.lock").exists());

        let outcome = stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &["f.txt".into()],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        assert_eq!(outcome.staged_lines["f.txt"], ["1-15"]);
        assert!(!root.join(".git/index.lock").exists());
        let index = repo.index_handle().load().unwrap();
        let staged = repo
            .odb()
            .read(&index.get(b"f.txt", 0).unwrap().oid)
            .unwrap()
            .data;
        let expected: String = base
            .lines()
            .enumerate()
            .map(|(i, l)| {
                if i < 15 && i % 10 == 0 {
                    format!("{}\n", l.to_uppercase())
                } else {
                    format!("{l}\n")
                }
            })
            .collect();
        assert_eq!(String::from_utf8(staged).unwrap(), expected);
        let other = repo
            .odb()
            .read(&index.get(b"other.txt", 0).unwrap().oid)
            .unwrap()
            .data;
        assert_eq!(other, b"other\n", "unselected paths stay unstaged");
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_with_literal_pathspec_among_other_dirty_files_match_git() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let base = numbered_lines(300);
        std::fs::write(root.join("big.txt"), &base).unwrap();
        std::fs::create_dir_all(root.join("sub")).unwrap();
        for i in 0..20 {
            std::fs::write(root.join(format!("sub/f{i}.txt")), format!("{i}\n")).unwrap();
        }
        git(root, &["add", "."]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("big.txt"), edit_every_tenth_line(&base)).unwrap();
        std::fs::write(root.join("sub/f3.txt"), b"dirty\n").unwrap();
        stage_lines_and_compare_git(
            &repo,
            root,
            "big.txt",
            vec![
                LineRange {
                    path: "big.txt".into(),
                    start: 1,
                    end: 105,
                },
                LineRange {
                    path: "big.txt".into(),
                    start: 251,
                    end: 251,
                },
            ],
        );
        let out = Command::new("git")
            .current_dir(root)
            .args(["diff", "--name-only"])
            .output()
            .expect("git diff");
        let unstaged = String::from_utf8_lossy(&out.stdout);
        assert!(unstaged.lines().any(|l| l == "sub/f3.txt"), "{unstaged}");
        assert!(unstaged.lines().any(|l| l == "big.txt"), "{unstaged}");
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_on_top_of_staged_change_match_git() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let base = numbered_lines(100);
        std::fs::write(root.join("f.txt"), &base).unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        let edited = edit_every_tenth_line(&base);
        std::fs::write(root.join("f.txt"), &edited).unwrap();
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: Vec::new(),
                ranges: vec![LineRange {
                    path: "f.txt".into(),
                    start: 1,
                    end: 30,
                }],
            },
            &["f.txt".into()],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        git(root, &["commit", "-qm", "partial"]);
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &HunkSelection {
                ids: Vec::new(),
                ranges: vec![LineRange {
                    path: "f.txt".into(),
                    start: 31,
                    end: 60,
                }],
            },
            &["f.txt".into()],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        stage_lines_and_compare_git(
            &repo,
            root,
            "f.txt",
            vec![LineRange {
                path: "f.txt".into(),
                start: 61,
                end: 80,
            }],
        );
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_without_pathspec_match_git() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        let (base, edited) = three_hunk_body();
        std::fs::write(root.join("f.txt"), base).unwrap();
        std::fs::write(root.join("g.txt"), b"g\n").unwrap();
        git(root, &["add", "."]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), &edited).unwrap();
        std::fs::write(root.join("g.txt"), b"G\n").unwrap();
        let selection = HunkSelection {
            ids: Vec::new(),
            ranges: vec![LineRange {
                path: "f.txt".into(),
                start: 10,
                end: 30,
            }],
        };
        let patch = resolve_selection(&repo, DiffSide::Unstaged, &selection, &[], hunk_diff_opts())
            .unwrap();
        let patch_text: String = patch.iter().map(format_patch_for_git).collect();
        stage_hunks(
            &repo,
            DiffSide::Unstaged,
            &selection,
            &[],
            hunk_diff_opts(),
            false,
            &crate::progress::NeverCancel,
        )
        .unwrap();
        let grit_tree =
            write_tree_from_index(repo.odb(), &repo.index_handle().load().unwrap(), "").unwrap();
        git(root, &["read-tree", "HEAD"]);
        let patch_path = root.join("partial.diff");
        std::fs::write(&patch_path, patch_text).unwrap();
        git(root, &["apply", "--cached", patch_path.to_str().unwrap()]);
        let git_tree = Command::new("git")
            .current_dir(root)
            .args(["write-tree"])
            .output()
            .expect("write-tree");
        assert_eq!(
            grit_tree.to_hex(),
            String::from_utf8_lossy(&git_tree.stdout).trim()
        );
        git(root, &["fsck"]);
    }

    #[cfg_attr(
        not(feature = "full-tests"),
        ignore = "starts system git or is heavy; run with --features full-tests"
    )]
    #[test]
    fn lines_no_eof_newline() {
        let (dir, repo) = init_repo();
        let root = dir.path();
        std::fs::write(root.join("f.txt"), b"old").unwrap();
        git(root, &["add", "f.txt"]);
        git(root, &["commit", "-qm", "init"]);
        std::fs::write(root.join("f.txt"), b"new").unwrap();
        stage_lines_and_compare_git(
            &repo,
            root,
            "f.txt",
            vec![LineRange {
                path: "f.txt".into(),
                start: 1,
                end: 1,
            }],
        );
    }
}