marver 0.0.11

//! A thin wrapper over the `git` CLI.
//!
//! Shelling out rather than linking libgit2: worktree support is the feature
//! marver leans on hardest, and the CLI is the reference implementation of it.
//!
//! Every call is local. Nothing here fetches, and `GIT_TERMINAL_PROMPT=0` is set
//! so a repo with a credential-requiring remote fails fast instead of hanging on
//! a prompt no TUI could answer.

use std::ffi::OsStr;
use std::path::{Path, PathBuf};
use std::process::Command;

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("could not run git: {0}")]
    Spawn(#[source] std::io::Error),
    #[error("git {args} failed in {repo}: {stderr}")]
    Failed {
        repo: PathBuf,
        args: String,
        stderr: String,
    },
    #[error("{0} has no default branch and no checked-out branch")]
    NoDefaultBranch(PathBuf),
}

pub type Result<T> = std::result::Result<T, Error>;

/// Branches tried, in order, when the remote does not advertise a default.
const FALLBACK_DEFAULTS: &[&str] = &["main", "master", "trunk", "develop"];

/// Run git and return `(succeeded, stdout)` without judging the exit status.
///
/// Some git commands report a difference with a non-zero exit while still
/// producing the output we want — `diff --no-index` is the notable one.
fn output<S: AsRef<OsStr>>(repo: &Path, args: &[S]) -> Result<(bool, String)> {
    let result = Command::new("git")
        .arg("-C")
        .arg(repo)
        .args(args)
        .env("GIT_TERMINAL_PROMPT", "0")
        .output()
        .map_err(Error::Spawn)?;
    Ok((
        result.status.success(),
        String::from_utf8_lossy(&result.stdout).into_owned(),
    ))
}

/// Run git in `repo` and return stdout exactly as produced.
///
/// Callers parsing machine-readable output must use this rather than [`run`]:
/// `status --porcelain` lines begin with a significant space, which trimming
/// would silently eat, shifting every path by one character.
pub fn run_raw<S: AsRef<OsStr>>(repo: &Path, args: &[S]) -> Result<String> {
    let result = Command::new("git")
        .arg("-C")
        .arg(repo)
        .args(args)
        .env("GIT_TERMINAL_PROMPT", "0")
        .output()
        .map_err(Error::Spawn)?;

    if !result.status.success() {
        return Err(Error::Failed {
            repo: repo.to_path_buf(),
            args: args
                .iter()
                .map(|a| a.as_ref().to_string_lossy().into_owned())
                .collect::<Vec<_>>()
                .join(" "),
            stderr: String::from_utf8_lossy(&result.stderr).trim().to_string(),
        });
    }
    Ok(String::from_utf8_lossy(&result.stdout).into_owned())
}

/// Run git in `repo` and return trimmed stdout.
///
/// Convenient for single-value answers such as a branch name or a hash. For
/// anything parsed line-by-line, use [`run_raw`].
pub fn run<S: AsRef<OsStr>>(repo: &Path, args: &[S]) -> Result<String> {
    Ok(run_raw(repo, args)?.trim().to_string())
}

/// Like [`run`], but a non-zero exit is reported as `false` rather than an error.
fn succeeds<S: AsRef<OsStr>>(repo: &Path, args: &[S]) -> Result<bool> {
    match run(repo, args) {
        Ok(_) => Ok(true),
        Err(Error::Failed { .. }) => Ok(false),
        Err(other) => Err(other),
    }
}

pub fn is_repo(path: &Path) -> bool {
    run(path, &["rev-parse", "--git-dir"]).is_ok()
}

/// Whether a local branch of this name exists.
pub fn branch_exists(repo: &Path, branch: &str) -> Result<bool> {
    succeeds(
        repo,
        &[
            "show-ref",
            "--verify",
            "--quiet",
            &format!("refs/heads/{branch}"),
        ],
    )
}

/// The branch currently checked out, or `None` when HEAD is detached.
pub fn head_branch(repo: &Path) -> Result<Option<String>> {
    match run(repo, &["symbolic-ref", "--short", "--quiet", "HEAD"]) {
        Ok(branch) if !branch.is_empty() => Ok(Some(branch)),
        Ok(_) => Ok(None),
        Err(Error::Failed { .. }) => Ok(None),
        Err(other) => Err(other),
    }
}

/// The repository's default branch.
///
/// Resolution order, all of it local:
///
/// 1. What the remote advertises, via `refs/remotes/origin/HEAD`. Set by
///    `git clone`, so it is right for most repos and costs nothing.
/// 2. The first conventional name that actually exists — a repo cloned before
///    `origin/HEAD` was recorded, or one with no remote at all.
/// 3. Whatever is checked out, as a last resort.
///
/// Deliberately never fetches. Task branches cut from a possibly-stale local
/// default, which is what `git checkout main` would have given you anyway.
pub fn default_branch(repo: &Path) -> Result<String> {
    if let Ok(head) = run(
        repo,
        &["symbolic-ref", "--short", "refs/remotes/origin/HEAD"],
    ) && let Some(branch) = head.strip_prefix("origin/")
        && !branch.is_empty()
        && branch_exists(repo, branch)?
    {
        return Ok(branch.to_string());
    }

    for candidate in FALLBACK_DEFAULTS {
        if branch_exists(repo, candidate)? {
            return Ok((*candidate).to_string());
        }
    }

    head_branch(repo)?.ok_or_else(|| Error::NoDefaultBranch(repo.to_path_buf()))
}

/// Add a worktree at `path` on `branch`, creating it from `base` if it is new.
///
/// The existing-branch case is not an edge case. Stopping a task keeps its
/// branch by default, so the ordinary "stop it, keep the work, start it again"
/// path comes back here with the branch already present — and `-b` on an
/// existing branch is a hard error.
pub fn worktree_add(repo: &Path, path: &Path, branch: &str, base: &str) -> Result<()> {
    let mut args = vec![OsStr::new("worktree"), OsStr::new("add")];
    if !branch_exists(repo, branch)? {
        args.push(OsStr::new("-b"));
        args.push(OsStr::new(branch));
        args.push(path.as_os_str());
        args.push(OsStr::new(base));
    } else {
        // Checking out a branch that already exists: no base, or git would try
        // to reset it and discard whatever is on it.
        args.push(path.as_os_str());
        args.push(OsStr::new(branch));
    }
    run(repo, &args)?;
    Ok(())
}

/// Remove a worktree. `force` discards uncommitted changes in it.
pub fn worktree_remove(repo: &Path, path: &Path, force: bool) -> Result<()> {
    let mut args = vec![OsStr::new("worktree"), OsStr::new("remove")];
    if force {
        args.push(OsStr::new("--force"));
    }
    args.push(path.as_os_str());
    run(repo, &args)?;
    Ok(())
}

/// Drop administrative records for worktrees whose directories are gone.
pub fn worktree_prune(repo: &Path) -> Result<()> {
    run(repo, &["worktree", "prune"])?;
    Ok(())
}

/// Paths of every worktree attached to this repo, including the main one.
pub fn worktree_list(repo: &Path) -> Result<Vec<PathBuf>> {
    let out = run(repo, &["worktree", "list", "--porcelain"])?;
    Ok(out
        .lines()
        .filter_map(|line| line.strip_prefix("worktree "))
        .map(PathBuf::from)
        .collect())
}

/// One entry from `git status --porcelain`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct StatusEntry {
    /// Index status character. `?` means untracked.
    pub index: char,
    /// Working-tree status character.
    pub worktree: char,
    /// Path relative to the repository root.
    pub path: String,
    /// Where a renamed file came from.
    pub original: Option<String>,
}

impl StatusEntry {
    pub fn is_untracked(&self) -> bool {
        self.index == '?' && self.worktree == '?'
    }

    /// Whether there is something in the index to commit.
    pub fn is_staged(&self) -> bool {
        !self.is_untracked() && self.index != ' '
    }

    /// Whether the working tree differs from the index.
    pub fn is_unstaged(&self) -> bool {
        self.is_untracked() || self.worktree != ' '
    }

    /// Whether the file has an unresolved merge conflict.
    ///
    /// The codes git documents as unmerged: `DD`, `AU`, `UD`, `UA`, `DU`, `AA`,
    /// `UU`. A `U` in either column is the reliable marker, plus the two
    /// same-letter pairs that have no `U` at all.
    pub fn is_unmerged(&self) -> bool {
        self.index == 'U'
            || self.worktree == 'U'
            || matches!((self.index, self.worktree), ('D', 'D') | ('A', 'A'))
    }
}

/// Everything changed in a worktree, staged and not.
///
/// Uses `-z` rather than the human format: git quotes and escapes paths
/// containing spaces, quotes, or newlines in the default output, and unquoting
/// that correctly is harder than reading NUL-separated records. `-uall` lists
/// files inside new directories individually rather than collapsing them to the
/// directory, which would otherwise hide every file an agent created.
pub fn status(repo: &Path) -> Result<Vec<StatusEntry>> {
    let out = run_raw(repo, &["status", "--porcelain=v1", "-z", "-uall"])?;
    Ok(parse_status(&out))
}

fn parse_status(raw: &str) -> Vec<StatusEntry> {
    let mut entries = Vec::new();
    // Records are NUL-separated; a rename spends two records, the second being
    // the original path.
    let mut records = raw.split('\0').filter(|r| !r.is_empty());
    while let Some(record) = records.next() {
        let mut chars = record.chars();
        let (Some(index), Some(worktree)) = (chars.next(), chars.next()) else {
            continue;
        };
        let path = record.get(3..).unwrap_or_default().to_string();
        // Either column can carry the rename. `git status` documents " R" as
        // "renamed in work tree", which `git add -N` produces routinely — and
        // the second record is consumed either way. Checking only the index
        // column left the origin path to be read as the next entry, so a
        // phantom file appeared in the review list, reported itself as staged,
        // and errored on every attempt to stage or unstage it.
        let original = if matches!(index, 'R' | 'C') || matches!(worktree, 'R' | 'C') {
            records.next().map(str::to_string)
        } else {
            None
        };
        entries.push(StatusEntry {
            index,
            worktree,
            path,
            original,
        });
    }
    entries
}

/// One exact path, as a pathspec git will not interpret.
///
/// Everything after `--` is still a *pathspec*, not a filename: `a?.txt`
/// matches `ab.txt` as well, and a backslash escapes the next character. A
/// filename is a literal, and saying so is the only way to mean it — otherwise
/// staging one file stages its neighbours, and asking for one file's diff can
/// return another file's.
fn literal(path: &str) -> String {
    format!(":(literal){path}")
}

/// Unified diff for a worktree. `staged` reads the index instead of the tree.
pub fn diff(repo: &Path, path: Option<&str>, staged: bool) -> Result<String> {
    let mut args: Vec<String> = vec!["diff".into()];
    if staged {
        args.push("--cached".into());
    }
    // Never colour or page: this is parsed, not read by a human here.
    args.extend(["--no-color".to_string(), "--no-ext-diff".to_string()]);
    if let Some(path) = path {
        args.push("--".into());
        args.push(literal(path));
    }
    let args: Vec<&str> = args.iter().map(String::as_str).collect();
    run_raw(repo, &args)
}

/// Diff of an untracked file against nothing, so new files are reviewable.
///
/// `git diff` ignores untracked files entirely; `--no-index` against
/// `/dev/null` produces the same shape as any other addition.
pub fn diff_untracked(repo: &Path, path: &str) -> Result<String> {
    // --no-index exits 1 whenever the files differ, which is always the case
    // here, so the exit status is ignored and stdout is what matters.
    let (_, out) = output(
        repo,
        &["diff", "--no-color", "--no-index", "--", "/dev/null", path],
    )?;
    Ok(out)
}

pub fn stage(repo: &Path, path: &str) -> Result<()> {
    run(repo, &["add", "--", &literal(path)])?;
    Ok(())
}

pub fn stage_all(repo: &Path) -> Result<()> {
    run(repo, &["add", "-A"])?;
    Ok(())
}

/// Remove a path from the index, leaving the working tree untouched.
pub fn unstage(repo: &Path, path: &str) -> Result<()> {
    run(repo, &["restore", "--staged", "--", &literal(path)])?;
    Ok(())
}

pub fn has_staged_changes(repo: &Path) -> Result<bool> {
    // Exits 1 when there are differences, which is not a failure here.
    Ok(!succeeds(repo, &["diff", "--cached", "--quiet"])?)
}

/// Commit the index. Returns the new commit's short hash.
pub fn commit(repo: &Path, message: &str) -> Result<String> {
    run(repo, &["commit", "-m", message])?;
    run(repo, &["rev-parse", "--short", "HEAD"])
}

/// Delete a local branch. `force` deletes even if unmerged.
pub fn branch_delete(repo: &Path, branch: &str, force: bool) -> Result<()> {
    let flag = if force { "-D" } else { "-d" };
    run(repo, &["branch", flag, branch])?;
    Ok(())
}

#[cfg(test)]
pub(crate) mod testing {
    use super::*;
    use std::path::Path;

    /// Initialise a repo with one commit on `default_branch`.
    pub fn init_repo(path: &Path, default_branch: &str) {
        std::fs::create_dir_all(path).expect("create repo dir");
        let init = Command::new("git")
            .arg("-C")
            .arg(path)
            .args(["init", "-q", "-b", default_branch])
            .output()
            .expect("git init");
        assert!(init.status.success(), "git init failed");

        run(path, &["config", "user.email", "test@marver.invalid"]).unwrap();
        run(path, &["config", "user.name", "marver tests"]).unwrap();
        std::fs::write(path.join("README.md"), "# test\n").expect("write file");
        run(path, &["add", "."]).unwrap();
        run(path, &["commit", "-q", "-m", "initial"]).unwrap();
    }

    /// Point `refs/remotes/origin/HEAD` at a branch, as `git clone` would.
    pub fn set_origin_head(path: &Path, branch: &str) {
        run(
            path,
            &[
                "update-ref",
                &format!("refs/remotes/origin/{branch}"),
                "HEAD",
            ],
        )
        .unwrap();
        run(
            path,
            &[
                "symbolic-ref",
                "refs/remotes/origin/HEAD",
                &format!("refs/remotes/origin/{branch}"),
            ],
        )
        .unwrap();
    }
}

#[cfg(test)]
mod tests {
    use super::testing::*;
    use super::*;
    use tempfile::TempDir;

    #[test]
    fn detects_a_repo() {
        let tmp = TempDir::new().unwrap();
        let repo = tmp.path().join("r");
        init_repo(&repo, "main");
        assert!(is_repo(&repo));

        let plain = tmp.path().join("plain");
        std::fs::create_dir_all(&plain).unwrap();
        assert!(!is_repo(&plain));
    }

    #[test]
    fn reads_the_checked_out_branch() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "trunk");
        assert_eq!(head_branch(tmp.path()).unwrap().as_deref(), Some("trunk"));
    }

    #[test]
    fn branch_existence_is_reported_not_errored() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        assert!(branch_exists(tmp.path(), "main").unwrap());
        assert!(!branch_exists(tmp.path(), "nope").unwrap());
    }

    #[test]
    fn default_branch_prefers_what_the_remote_advertises() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        // A repo whose remote says "develop" even though main exists locally.
        run(tmp.path(), &["branch", "develop"]).unwrap();
        set_origin_head(tmp.path(), "develop");

        assert_eq!(default_branch(tmp.path()).unwrap(), "develop");
    }

    #[test]
    fn default_branch_falls_back_to_conventional_names() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "master");
        // No origin/HEAD at all, as in a repo created locally.
        assert_eq!(default_branch(tmp.path()).unwrap(), "master");
    }

    #[test]
    fn default_branch_falls_back_to_head_for_unconventional_names() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "shipping");
        assert_eq!(default_branch(tmp.path()).unwrap(), "shipping");
    }

    #[test]
    fn a_stale_origin_head_does_not_win() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        // origin/HEAD points at a branch that no longer exists locally.
        run(
            tmp.path(),
            &["update-ref", "refs/remotes/origin/gone", "HEAD"],
        )
        .unwrap();
        run(
            tmp.path(),
            &[
                "symbolic-ref",
                "refs/remotes/origin/HEAD",
                "refs/remotes/origin/gone",
            ],
        )
        .unwrap();
        run(
            tmp.path(),
            &["update-ref", "-d", "refs/remotes/origin/gone"],
        )
        .unwrap();

        assert_eq!(
            default_branch(tmp.path()).unwrap(),
            "main",
            "should skip a default that has no local branch"
        );
    }

    #[test]
    fn adds_and_removes_a_worktree() {
        let tmp = TempDir::new().unwrap();
        let repo = tmp.path().join("repo");
        init_repo(&repo, "main");
        let wt = tmp.path().join("wt");

        worktree_add(&repo, &wt, "feature", "main").unwrap();
        assert!(wt.join("README.md").exists());
        assert!(branch_exists(&repo, "feature").unwrap());
        assert!(
            worktree_list(&repo)
                .unwrap()
                .iter()
                .any(|p| p.ends_with("wt"))
        );

        worktree_remove(&repo, &wt, false).unwrap();
        assert!(!wt.exists());
        assert!(
            branch_exists(&repo, "feature").unwrap(),
            "removing a worktree must not delete its branch"
        );
    }

    #[test]
    fn a_dirty_worktree_needs_force() {
        let tmp = TempDir::new().unwrap();
        let repo = tmp.path().join("repo");
        init_repo(&repo, "main");
        let wt = tmp.path().join("wt");
        worktree_add(&repo, &wt, "feature", "main").unwrap();
        std::fs::write(wt.join("README.md"), "changed\n").unwrap();

        assert!(worktree_remove(&repo, &wt, false).is_err());
        worktree_remove(&repo, &wt, true).unwrap();
        assert!(!wt.exists());
    }

    #[test]
    fn a_duplicate_branch_is_an_error() {
        let tmp = TempDir::new().unwrap();
        let repo = tmp.path().join("repo");
        init_repo(&repo, "main");
        worktree_add(&repo, &tmp.path().join("a"), "feature", "main").unwrap();

        let err = worktree_add(&repo, &tmp.path().join("b"), "feature", "main").unwrap_err();
        assert!(matches!(err, Error::Failed { .. }));
    }

    #[test]
    fn failures_carry_stderr() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        let err = run(tmp.path(), &["rev-parse", "does-not-exist"]).unwrap_err();
        let Error::Failed { stderr, args, .. } = err else {
            panic!("expected a command failure");
        };
        assert!(!stderr.is_empty(), "stderr should be captured");
        assert!(args.contains("rev-parse"));
    }

    #[test]
    fn status_keeps_the_leading_space_that_encodes_the_index() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        std::fs::write(tmp.path().join("README.md"), "changed\n").unwrap();

        let entries = status(tmp.path()).unwrap();
        assert_eq!(entries.len(), 1);
        // " M README.md": trimming stdout would eat the leading space and
        // shift every path by one character.
        assert_eq!(entries[0].index, ' ');
        assert_eq!(entries[0].worktree, 'M');
        assert_eq!(entries[0].path, "README.md");
        assert!(entries[0].is_unstaged() && !entries[0].is_staged());
    }

    #[test]
    fn status_distinguishes_staged_untracked_and_renamed() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        std::fs::write(tmp.path().join("staged.txt"), "s\n").unwrap();
        stage(tmp.path(), "staged.txt").unwrap();
        std::fs::write(tmp.path().join("loose.txt"), "l\n").unwrap();
        run(tmp.path(), &["mv", "README.md", "RENAMED.md"]).unwrap();

        let entries = status(tmp.path()).unwrap();
        let by_path = |p: &str| entries.iter().find(|e| e.path == p).cloned();

        let staged = by_path("staged.txt").expect("staged.txt");
        assert_eq!(staged.index, 'A');
        assert!(staged.is_staged());

        let loose = by_path("loose.txt").expect("loose.txt");
        assert!(loose.is_untracked());
        assert!(loose.is_unstaged() && !loose.is_staged());

        let renamed = by_path("RENAMED.md").expect("RENAMED.md");
        assert_eq!(renamed.index, 'R');
        assert_eq!(
            renamed.original.as_deref(),
            Some("README.md"),
            "a rename spends two NUL records; the second is where it came from"
        );

        // Looking entries up by path cannot see an entry that should not be
        // there. A desync produces exactly that, so the count is asserted too.
        assert_eq!(entries.len(), 3, "no phantom entries: {entries:?}");
    }

    #[test]
    fn a_rename_in_the_work_tree_does_not_desync_the_parser() {
        // `git add -N` on a moved file gives " R", with the rename in the
        // *worktree* column rather than the index. It still spends two NUL
        // records. Checking only the index column left the origin path to be
        // read as the next entry: a phantom file appeared in the review list,
        // claimed to be staged, and errored on every attempt to touch it.
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        std::fs::write(tmp.path().join("old.txt"), "one\n").unwrap();
        stage_all(tmp.path()).unwrap();
        run(tmp.path(), &["commit", "-q", "-m", "seed"]).unwrap();

        std::fs::rename(tmp.path().join("old.txt"), tmp.path().join("new.txt")).unwrap();
        run(tmp.path(), &["add", "-N", "new.txt"]).unwrap();

        let entries = status(tmp.path()).unwrap();
        assert_eq!(entries.len(), 1, "one rename, one entry: {entries:?}");
        assert_eq!(entries[0].path, "new.txt");
        assert_eq!(entries[0].worktree, 'R');
        assert_eq!(entries[0].original.as_deref(), Some("old.txt"));
    }

    #[test]
    fn staged_changes_are_detectable_and_committable() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        assert!(!has_staged_changes(tmp.path()).unwrap());

        std::fs::write(tmp.path().join("new.txt"), "n\n").unwrap();
        stage(tmp.path(), "new.txt").unwrap();
        assert!(has_staged_changes(tmp.path()).unwrap());

        let hash = commit(tmp.path(), "add new").unwrap();
        assert!(!hash.is_empty());
        assert!(!has_staged_changes(tmp.path()).unwrap());
        assert_eq!(
            run(tmp.path(), &["log", "-1", "--pretty=%s"]).unwrap(),
            "add new"
        );
    }

    #[test]
    fn unstaging_leaves_the_file_on_disk() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        std::fs::write(tmp.path().join("README.md"), "changed\n").unwrap();
        stage(tmp.path(), "README.md").unwrap();
        unstage(tmp.path(), "README.md").unwrap();

        assert!(!has_staged_changes(tmp.path()).unwrap());
        assert_eq!(
            std::fs::read_to_string(tmp.path().join("README.md")).unwrap(),
            "changed\n",
            "unstaging must not discard the work"
        );
    }

    #[test]
    fn a_glob_in_a_filename_stages_only_that_file() {
        // Everything after `--` is a pathspec, not a filename. Staging
        // `a?.txt` used to stage `ab.txt` and `ax.txt` along with it, so a
        // commit carried changes the user never reviewed.
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        for name in ["a?.txt", "ab.txt", "ax.txt"] {
            std::fs::write(tmp.path().join(name), "content\n").unwrap();
        }

        stage(tmp.path(), "a?.txt").unwrap();

        let staged: Vec<String> = status(tmp.path())
            .unwrap()
            .into_iter()
            .filter(|e| e.is_staged())
            .map(|e| e.path)
            .collect();
        assert_eq!(staged, ["a?.txt"], "only the named file may be staged");
    }

    #[test]
    fn a_glob_in_a_filename_unstages_only_that_file() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        for name in ["a*.txt", "ab.txt"] {
            std::fs::write(tmp.path().join(name), "content\n").unwrap();
        }
        stage_all(tmp.path()).unwrap();

        unstage(tmp.path(), "a*.txt").unwrap();

        let staged: Vec<String> = status(tmp.path())
            .unwrap()
            .into_iter()
            .filter(|e| e.is_staged())
            .map(|e| e.path)
            .collect();
        assert_eq!(staged, ["ab.txt"], "the neighbour must stay staged");
    }

    #[test]
    fn a_glob_in_a_filename_diffs_only_that_file() {
        // The worst of the three: the review screen takes the first file out of
        // the diff, so the user read one file's changes and committed another's.
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        for name in ["a?.txt", "a0.txt"] {
            std::fs::write(tmp.path().join(name), "before\n").unwrap();
        }
        stage_all(tmp.path()).unwrap();
        run(tmp.path(), &["commit", "-q", "-m", "seed"]).unwrap();
        std::fs::write(tmp.path().join("a?.txt"), "QUESTION\n").unwrap();
        std::fs::write(tmp.path().join("a0.txt"), "ZERO\n").unwrap();

        let out = diff(tmp.path(), Some("a?.txt"), false).unwrap();
        assert!(out.contains("QUESTION"), "wanted the named file: {out}");
        assert!(
            !out.contains("ZERO"),
            "another file's changes must not appear: {out}"
        );
    }

    #[test]
    fn branches_can_be_deleted() {
        let tmp = TempDir::new().unwrap();
        init_repo(tmp.path(), "main");
        run(tmp.path(), &["branch", "scratch"]).unwrap();
        branch_delete(tmp.path(), "scratch", true).unwrap();
        assert!(!branch_exists(tmp.path(), "scratch").unwrap());
    }
}