monochromatic-git-policy-cli 0.5.0

//! What:
//!  The authoritative ref updates a `git push` would send, discovered by a dry-run push whose report Git writes itself.
//! Why:
//!  The manual-push policies must scan exactly what Git would publish, so the probe asks Git:
//!  `git push --dry-run --porcelain` reports each destination and ref update (`manual_push_porcelain`), the local
//!  objects come from that report or from one `rev-parse`, and `git ls-remote --refs` confirms each destination value.
//!  A remote ref that changed between negotiation and confirmation stops the probe.
//!  No program of ours is started for this, and no hook or shell text is written: an earlier version recorded Git's
//!  update lines with a `#!/bin/sh` hook (`doc/planning/cli-git-no-self-invocation.md`).
//!  Every Git child here is bounded by the query deadline, so a remote that never answers cannot hold the push.
//!
//! In TS you'd write (pseudocode):
//! ```ts
//! const updates = await probeManualPushUpdates({ gitPath, cwd, args });
//! ```

/// The probe's Git runner, its bounded queries and its environment.
use super::auto_push_single_flight::{PushGit, run_query};
/// The destination Git would pick for a bare push, and the porcelain report's parser.
use super::lfs_upload_plan::resolve_push_remote;
use super::manual_push_porcelain::{PorcelainUpdate, RemoteBefore, parse_porcelain};
/// The push's own reading of its destination.
use super::command_push::push_shape;
/// Owned OS strings for the probe's Git arguments.
use std::ffi::OsString;

/// What:
///  Why the probe could not establish the updates Git would push.
/// Why:
///   Every variant stops the policy lifecycle with a content-unavailable failure; none guesses an update.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// class ManualPushProbeError extends Error {}
/// ```
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ManualPushProbeError {
    /// Diagnostic naming what could not be established.
    pub message: String,
}

impl std::fmt::Display for ManualPushProbeError {
    /// Writes the diagnostic text.
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        return formatter.write_str(&self.message);
    }
}

impl std::error::Error for ManualPushProbeError {}

/// Build a probe error from text.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// new ManualPushProbeError(message)
/// ```
fn probe_error(message: String) -> ManualPushProbeError {
    return ManualPushProbeError { message };
}

/// What:
///  One confirmed push update, the public fact the policies read.
/// Why:
///   An absent value is `None`, which replaces the incumbent's `ABSENT_GIT_VALUE` sentinel.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// type PushUpdate = { localOid: string | typeof ABSENT_GIT_VALUE; remoteOid: string | typeof ABSENT_GIT_VALUE; remoteName; remoteRef };
/// ```
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct PushUpdate {
    /// Local object name; `None` for a deletion.
    pub local_oid: Option<String>,
    /// Destination object name confirmed by `ls-remote`; `None` when the ref is absent.
    pub remote_oid: Option<String>,
    /// Destination remote name.
    pub remote_name: String,
    /// Destination ref.
    pub remote_ref: String,
}

/// What:
///  The probe's Git arguments: the invocation's global options, the switches that keep every hook and full object
///  names, then `push` with `--dry-run --porcelain` placed before any `--` terminator.
/// Why:
///   The `--` terminator is the user's; the options Git interprets must stay before it. The probe publishes nothing and
///  must not run the upload hook of the caller's configuration, so configured `pre-push` hooks are off and the
///  traditional hooks directory is one that never exists.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// probeArgs({ globalPrefix, args });
/// ```
pub fn probe_arguments(global_prefix: &[OsString], post_subcommand: &[OsString]) -> Vec<OsString> {
    let separator = post_subcommand.iter().position(|argument| {
        return argument.as_os_str() == "--";
    });
    let insertion = separator.unwrap_or(post_subcommand.len());
    let mut arguments: Vec<OsString> = global_prefix.to_vec();
    for setting in [
        format!("core.hooksPath={}", super::hooks_off::NO_HOOKS_DIRECTORY),
        String::from("hook.pre-push.enabled=false"),
        String::from("core.abbrev=no"),
    ] {
        arguments.push(OsString::from("-c"));
        arguments.push(OsString::from(setting));
    }
    arguments.push(OsString::from("push"));
    arguments.extend(post_subcommand[..insertion].iter().cloned());
    // A `-q` written by the caller silences the report this probe reads, so it is cancelled here; the caller's own
    //  push keeps its `-q`.
    arguments.push(OsString::from("--no-quiet"));
    arguments.push(OsString::from("--dry-run"));
    arguments.push(OsString::from("--porcelain"));
    arguments.extend(post_subcommand[insertion..].iter().cloned());
    return arguments;
}

/// One Git query of the probe: its trimmed standard output when it exits with status zero.
fn answer(git: &PushGit, arguments: &[OsString]) -> Option<String> {
    let output = run_query(git, arguments).ok()?;
    if output.code != Some(0) {
        return None;
    }
    return Some(String::from_utf8_lossy(output.stdout.as_slice()).trim().to_owned());
}

/// The destination locations of a remote name, one per `To` block Git printed: the push URLs of a configured remote,
///  or the name itself when it is not one (a URL or a path typed in place of a remote).
fn locations_of(git: &PushGit, global_prefix: &[OsString], remote: &str) -> Vec<String> {
    let mut arguments: Vec<OsString> = global_prefix.to_vec();
    arguments.extend(["remote", "get-url", "--push", "--all", remote].map(OsString::from));
    return match answer(git, arguments.as_slice()) {
        Some(listing) if !listing.is_empty() => listing.lines().map(str::to_owned).collect(),
        Some(_) | None => vec![remote.to_owned()],
    };
}

/// What:
///  The object names of local refs, in order, from one `rev-parse`.
/// Why:
///   A new ref's report line has no object name; the ref's own value is what the push sends.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// (await git(['rev-parse', ...names])).split('\n')
/// ```
fn local_objects(git: &PushGit, global_prefix: &[OsString], names: &[&str]) -> Result<Vec<String>, ManualPushProbeError> {
    if names.is_empty() {
        return Ok(Vec::new());
    }
    let mut arguments: Vec<OsString> = global_prefix.to_vec();
    arguments.push(OsString::from("rev-parse"));
    arguments.extend(names.iter().map(OsString::from));
    let listing: String = answer(git, arguments.as_slice())
        .ok_or_else(|| {
            return probe_error(format!("the local objects of {names:?} could not be read"));
        })?;
    let objects: Vec<String> = listing.lines().map(str::to_owned).collect();
    if objects.len() != names.len() {
        return Err(probe_error(format!("rev-parse answered {} names for {}", objects.len(), names.len())));
    }
    return Ok(objects);
}

/// What:
///  Confirm one destination's values with `git ls-remote --refs` and turn each reported update into a public update.
/// Why:
///   A destination that changed after the dry run reported would publish something the scan did not see, so a
///  mismatch between the report and the confirmation is an error, never a silent repair. A report that did not state the
///  remote's value (a deletion, a refusal) is taken from the confirmation alone.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// async function resolveRemoteGroup({ gitPath, cwd, remoteLocation, updates }): Promise<PushUpdate[]>;
/// ```
pub fn confirm_group(
    git: &PushGit,
    remote_location: &str,
    remote_name: &str,
    updates: &[(PorcelainUpdate, Option<String>)],
) -> Result<Vec<PushUpdate>, ManualPushProbeError> {
    let mut arguments: Vec<OsString> = vec![
        OsString::from("ls-remote"),
        OsString::from("--refs"),
        OsString::from(remote_location),
    ];
    arguments.extend(updates.iter().map(|(update, _local)| {
        return OsString::from(&update.to);
    }));
    let output = run_query(git, arguments.as_slice())
        .map_err(|error| {
            return probe_error(format!("ls-remote of {remote_location} failed: {error}"));
        })?;
    if output.code != Some(0) {
        return Err(probe_error(format!(
            "ls-remote of {remote_location} failed: {}",
            String::from_utf8_lossy(&output.stderr).trim_end()
        )));
    }
    let listing: String = String::from_utf8_lossy(&output.stdout).into_owned();
    let mut confirmed: Vec<PushUpdate> = Vec::new();
    for (update, local) in updates {
        let authoritative: Option<String> = listing.lines().find_map(|line| {
            return line.split_once('\t').filter(|(_oid, name)| {
                return *name == update.to;
            }).map(|(oid, _name)| {
                return oid.to_owned();
            });
        });
        let changed: bool = match &update.before {
            RemoteBefore::Absent => authoritative.is_some(),
            RemoteBefore::Known(reported) => authoritative.as_ref() != Some(reported),
            RemoteBefore::Unknown => false,
        };
        if changed {
            return Err(probe_error(format!("Remote ref changed during manual-push discovery: {}", update.to)));
        }
        confirmed.push(PushUpdate {
            local_oid: local.clone(),
            remote_oid: authoritative,
            remote_name: remote_name.to_owned(),
            remote_ref: update.to.clone(),
        });
    }
    return Ok(confirmed);
}

/// What:
///  Discover the exact updates the push would send, confirmed against each destination.
/// Why:
///   The lifecycle's candidates and published-set reads both start from these updates.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// async function probeManualPushUpdates({ gitPath, cwd, args }): Promise<PushUpdate[]>;
/// ```
pub fn probe_manual_push_updates(
    git: &PushGit,
    global_prefix: &[OsString],
    post_subcommand: &[OsString],
) -> Result<Vec<PushUpdate>, ManualPushProbeError> {
    let arguments: Vec<OsString> = probe_arguments(global_prefix, post_subcommand);
    let output = run_query(git, arguments.as_slice()).map_err(|error| {
        return probe_error(format!("probe push could not run: {error}"));
    })?;
    let report: String = String::from_utf8_lossy(output.stdout.as_slice()).into_owned();
    let blocks = parse_porcelain(report.as_str()).map_err(probe_error)?;
    if blocks.is_empty() {
        if output.code == Some(0) {
            return Ok(Vec::new());
        }
        return Err(probe_error(format!(
            "Git could not determine push updates: {}",
            String::from_utf8_lossy(&output.stderr).trim_end()
        )));
    }
    let named = push_shape(post_subcommand).and_then(|shape| {
        return shape.repository;
    });
    let mut asking = |query: &[&str]| -> Option<String> {
        let mut owned: Vec<OsString> = global_prefix.to_vec();
        owned.extend(query.iter().map(OsString::from));
        return answer(git, owned.as_slice());
    };
    let remote_name: String = resolve_push_remote(named, &mut asking).to_string_lossy().into_owned();
    // The location Git printed for a single destination is the push URL after every rewrite; it is used as it is
    //  unless it could have had credentials removed (an `@` in a URL is where they were), which costs one query.
    let locations: Vec<String> = match blocks.as_slice() {
        [only] if !only.shown.contains('@') => vec![only.shown.clone()],
        _ => locations_of(git, global_prefix, remote_name.as_str()),
    };
    if locations.len() != blocks.len() {
        return Err(probe_error(format!(
            "Git reported {} destinations but {remote_name} has {} push locations",
            blocks.len(),
            locations.len()
        )));
    }
    let mut confirmed: Vec<PushUpdate> = Vec::new();
    for (block, location) in blocks.iter().zip(locations.iter()) {
        let unnamed: Vec<&str> = block
            .updates
            .iter()
            .filter(|update| {
                return !update.from.is_empty() && update.after.is_none();
            })
            .map(|update| {
                return update.from.as_str();
            })
            .collect();
        let mut resolved = local_objects(git, global_prefix, unnamed.as_slice())?.into_iter();
        let group: Vec<(PorcelainUpdate, Option<String>)> = block
            .updates
            .iter()
            .map(|update| {
                let local: Option<String> = if update.from.is_empty() {
                    None
                } else {
                    update.after.clone().or_else(|| {
                        return resolved.next();
                    })
                };
                return (update.clone(), local);
            })
            .collect();
        confirmed.extend(confirm_group(git, location.as_str(), remote_name.as_str(), group.as_slice())?);
    }
    return Ok(confirmed);
}

/// The probe's arguments and its confirmation rules are controlled in the test module.
#[cfg(test)]
#[path = "manual_push_probe_tests.rs"]
mod tests;