monochromatic-git-policy-cli 0.6.0

//! What:
//!  The commit command's path through the resident service: prepare the commit in this process (private index,
//!  policies), send the prepared change to the service, and report what it landed.
//! Why:
//!  The service is the only writer, so a commit takes no lock and polls nothing: preparation and policies run here,
//!  outside the service's serialized step, and the service moves the branch once for a whole batch of commits
//!  (`doc/planning/cli-git-resident-service.md`, "Where preparation and policies run").
//!  Every command line lands through it. The lines `service_commit_args.rs` accepts are built here from the command line
//!  (message and identity options, sign-off, trailers, a reused or fixup message, `-a`, an index commit, `--amend`); every
//!  other line, and every commit that is not on an ordinary branch with an ordinary state, is built by real Git in a scratch
//!  repository and landed as Git made it. Which route a commit takes is decided by `service_route.rs`; what is prepared is
//!  `service_prepare.rs`.
//!
//! In TS you'd write (pseudocode):
//! ```ts
//! const result = await tryServiceCommit(invocation, checks, request); // undefined only when no service can be reached
//! ```

use crate::service_commit_input_notes_and_embedded_commit::managed_client_config;
use crate::service_server::Bind;
use crate::service_provision::ProvisionHost;
use crate::service_commit_input_notes_and_embedded_commit::route_for_this_worktree;
use crate::service_commit_input_notes_and_embedded_commit::{Embedded, arguments_after_subcommand, embedded_commit, standard_input_for, switched_branch_name};
use crate::service_commit_requests_and_landing_report::{report_landing, request_for_embedded, request_for_git_built};
use crate::commit_timing::CommitTiming;
use crate::private_index_request::indexed_request;
use crate::commit_transaction::{CommitInvocation, TransactionResult, TransactionStop, failed};
use crate::diagnostic_log::warn;
use crate::policy_checks::ShippedChecks;
use crate::policy_engine::StageRequest;
use crate::random_id::random_uuid;
use crate::repository_facts::RepositoryFacts;
use crate::scratch_location::SCRATCH_REFRESH_EVERY;
use crate::service_client::{ClientConfig, FreshScratch, ScratchWatch, Submitted, submit_traced, watch_scratch};
use crate::service_commit_args::{opens_editor, parse_service_commit, with_fixed_message};
use crate::service_handoff::ServiceHandoff;
use crate::service_land::LANDING_ATTEMPTS;
use crate::service_messages::{ClientFailure, render};
use crate::service_native::{BuildInput, GitBuilt, build_with_git};
use crate::service_prepare::{NativeInputs, PrepareInputs, Prepared, Ready, prepare};
use crate::service_replay::{Captured, Retry, conflict_result, retry_of};
use crate::service_protocol::CommitRequest;
use crate::service_provision::provision;
use crate::service_pruned::{content_was_removed, prepared_content_missing, reach_service_phase};
use crate::transaction_phase::Phase;
use crate::transaction_git::run_git_checked;
use std::ffi::OsString;
use std::path::{Path, PathBuf};
use std::time::Instant;

/// What the service path returns: the transaction result for the lifecycle, and the handoff when the commit landed.
pub struct ServiceCommit {
    /// What the policies and the landing came to.
    pub result: TransactionResult,
    /// How to leave the after-commit work for the service; absent when nothing landed.
    pub handoff: Option<ServiceHandoff>,
}

/// How many times a commit Git built is built again on the new tip when the branch moves before it lands, before the
///  plain failure. A build is one signature, so the bound keeps a busy branch from keeping a person's command running.
pub const REBUILD_ATTEMPTS: usize = 5;

/// The plain failure of a branch that moved under a commit that cannot be made again on another tip.
fn branch_moved(ready: &Ready) -> TransactionStop {
    let branch: String = ready.reference.trim_start_matches("refs/heads/").to_string();
    return TransactionStop::Message(render(&ClientFailure::BranchMoved { branch }));
}

/// What:
///  A path as text for a message.
/// Why:
///  A failure names the file a typed message was saved in.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// const displayText = (file: string) => file;
/// ```
fn display_text(file: &Path) -> String {
    return file.display().to_string();
}

/// What:
///  Lands the commit through the service, for every command line.
/// Why:
///   The service is the only writer of a commit. A machine where none can be reached or started ends the command with the
///  plain message of its platform, before anything was changed; every other ending is the commit's.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// await serviceCommit(invocation, checks, request, timing)
/// ```
pub fn service_commit<F: RepositoryFacts>(
    invocation: &CommitInvocation<'_>,
    checks: &mut ShippedChecks<F>,
    request: &StageRequest,
    timing: &mut CommitTiming,
) -> Result<ServiceCommit, TransactionStop> {
    let (address, provisioning): (Bind, Option<ProvisionHost>) = route_for_this_worktree(invocation, timing)?;
    let after: &[OsString] = arguments_after_subcommand(invocation.arguments, invocation.subcommand_index);
    let id: String = match random_uuid() {
        Ok(made) => made,
        Err(error) => return Err(failed(format!("an identity for this commit could not be made: {error:?}"))),
    };
    // The identity is the key that joins this commit's timing record to the service's journal entry for it.
    timing.request = Some(id.clone());
    let standard_input: Option<Vec<u8>> = standard_input_for(invocation)?;
    let mut provisioned: bool = false;
    // Whether an editor may have run, which decides what a moved branch costs the person: a message to keep or a signature to redo.
    let editor_possible: bool = opens_editor(after);
    let config: ClientConfig = managed_client_config(address, provisioning.as_ref());
    let scratch_name: String = format!("monochromatic-git-policy-cli-service-{id}");
    // The service builds the commits it can from the command line; real Git builds the rest in a scratch repository. Which
    //  it is gets decided once the preparation has passed every cheap decision (head, configuration, index, policies), so a
    //  commit the service never takes starts no Git for a message or an identity.
    let mut embedded: Option<Embedded> = None;
    let mut decided: bool = false;
    // The message the person typed once the editor has run, kept in a file so a commit moved by a tip that changed is built again from it.
    let mut fixed_message: Option<PathBuf> = None;
    // The message of the command as the last preparation settled it, kept for the person when the commit cannot be made.
    let mut last_message: Option<String> = None;
    // What the previous preparation captured when the service sent the commit back because the branch moved: the next
    //  preparation merges it onto the branch as it is and never reads the worktree again.
    let mut retry: Option<Captured> = None;
    // The branch (or `HEAD`) the first preparation found, which every later preparation must find again.
    let mut first_reference: Option<String> = None;
    // The commit's scratch directory, handed to the service once the first preparation made it: the service removes it when this
    //  command ends, and when this process is killed, because the connection closes either way. Without a service of this
    //  release to take it, the directory is removed here as before.
    let mut scratch_watch: Option<ScratchWatch> = None;
    // The commits Git built that the branch moving made useless: Git printed a summary for each, so the wrapper names them
    //  once the commit that did land is known.
    let mut unlanded: Vec<String> = Vec::new();
    for attempt in 0..REBUILD_ATTEMPTS {
        // A rebuild replays what the batches that landed meanwhile captured; the first try replays nothing.
        let mut replay: Option<Retry<'_>> = None;
        if let Some(captured) = retry.as_ref() {
            replay = Some(Retry { captured, attempt: u64::try_from(attempt).unwrap_or(u64::MAX) });
        }
        let inputs: PrepareInputs<'_> = PrepareInputs {
            scratch_name: scratch_name.as_str(),
            allow_empty: invocation.region.allow_empty,
            standard_input: standard_input.as_deref(),
            first: attempt == 0,
            replay,
        };
        let preparing: Instant = Instant::now();
        let prepared: Result<Prepared, TransactionStop> = prepare(invocation, checks, request, &inputs);
        timing.prepare += preparing.elapsed();
        timing.attempts += 1;
        let ready: Box<Ready> = match prepared? {
            Prepared::Conflict(conflict) => {
                // The message is kept so the person can commit again once their files agree with the commit that landed first.
                let saved: PathBuf = conflict.git_dir.join(format!("monochromatic-git-policy-cli-saved-message-{}", id.get(..8).unwrap_or(id.as_str())));
                // The typed message is kept beside the conflict when it can be written.
                let mut kept: Option<&PathBuf> = None;
                if let Some(text) = last_message.as_ref() {
                    match std::fs::write(&saved, text.as_str()) {
                        Ok(()) => kept = Some(&saved),
                        Err(error) => warn("serviceCommit", format!("saving the message failed: {error}").as_str()),
                    }
                }
                let result: TransactionResult = conflict_result(&conflict, kept.map(PathBuf::as_path));
                return Ok(ServiceCommit { result, handoff: None });
            }
            Prepared::Ended(result) => {
                // The policies could not read an object this commit had just written: something removed it meanwhile.
                //  The captured bytes are gone, and the worktree is not read again to replace them.
                if content_was_removed(result.events.as_slice()) {
                    return Err(TransactionStop::Message(render(&ClientFailure::ContentPruned)));
                }
                return Ok(ServiceCommit { result, handoff: None });
            }
            Prepared::Ready(ready) => ready,
        };
        // The branch the first preparation found. A worktree that switched since (the service refuses the landing, and a
        //  new preparation would read the new branch) is a failure like native Git's, with the typed message kept in its file.
        let building: Instant = Instant::now();
        if timing.reference.is_none() {
            timing.reference = Some(ready.reference.clone());
        }
        // The branch of the first preparation is the one every later preparation must be on.
        if first_reference.is_none() {
            first_reference = Some(ready.reference.clone());
        }
        let first_branch: String = match first_reference.as_ref() {
            Some(known) => known.clone(),
            None => ready.reference.clone(),
        };
        if first_branch != ready.reference {
            let failure: ClientFailure = ClientFailure::BranchSwitched {
                branch: switched_branch_name(first_branch.as_str()),
                now: switched_branch_name(ready.reference.as_str()),
                file: fixed_message.as_deref().map(display_text),
            };
            return Err(TransactionStop::Message(render(&failure)));
        }
        if scratch_watch.is_none() {
            scratch_watch = watch_scratch(&config, ready.inputs.capture.layout.git_dir.as_path(), ready.scratch.0.as_path());
        }
        if !decided {
            decided = true;
            if !ready.needs_native
                && let Some(parsed) = parse_service_commit(after)
            {
                embedded = embedded_commit(invocation, parsed)?;
            }
        }
        let native_inputs: &NativeInputs = &ready.inputs;
        // An amend the service builds is made from the commit `HEAD` named when the message was read; if the branch left it
        //  since, the amend is not made. Its tree is the private index's, and native Git refuses an amend that leaves the
        //  commit empty against its first parent (a merge excepted) unless `--allow-empty` says it is meant, which Git then
        //  says itself.
        let mut tree: Option<String> = None;
        if !ready.needs_native
            && let Some(made) = embedded.as_ref()
            && let Some(source) = made.source.as_ref()
        {
            if source.base != ready.base {
                return Err(branch_moved(&ready));
            }
            let written = run_git_checked(
                invocation.context,
                &indexed_request(
                    invocation.cwd,
                    &["write-tree"],
                    Some(native_inputs.commit_index.as_path()),
                    Some(native_inputs.capture.layout.object_directory.as_path()),
                ),
            )?;
            let written_tree: String = String::from_utf8_lossy(written.stdout.as_slice()).trim().to_string();
            let against: &str = source.parent_tree.as_deref().unwrap_or(native_inputs.capture.layout.empty_tree_oid.as_str());
            if source.parents.len() < 2 && !invocation.region.allow_empty && written_tree == against {
                embedded = None;
            } else {
                tree = Some(written_tree);
            }
        }
        let native: bool = ready.needs_native || embedded.is_none();
        // The embedded commit is used only when the native path is not taken.
        let embedded_in_use: Option<&Embedded> = if native { None } else { embedded.as_ref() };
        let mut typed: Option<String> = None;
        let (sent, first_parent): (CommitRequest, String) = match embedded_in_use {
            None => {
                let layout_prefix: usize = crate::global_arguments::global_layout(native_inputs.arguments.as_slice()).prefix_len;
                let rebuilt_arguments: Option<Vec<OsString>> = match fixed_message.as_deref() {
                    Some(file) => with_fixed_message(native_inputs.arguments.as_slice(), layout_prefix, file),
                    None => None,
                };
                let built: GitBuilt = build_with_git(&BuildInput {
                    context: invocation.context,
                    cwd: invocation.cwd,
                    capture: &native_inputs.capture,
                    scratch: ready.scratch.0.as_path(),
                    commit_index: native_inputs.commit_index.as_path(),
                    arguments: rebuilt_arguments.as_deref().unwrap_or(native_inputs.arguments.as_slice()),
                    pathspecs: native_inputs.pathspecs.as_slice(),
                    mode: native_inputs.mode,
                    staged_all: native_inputs.staged_all,
                    selected_privately: native_inputs.selected_privately,
                })?;
                let parent: String = built.parents.first().cloned().unwrap_or_default();
                typed = Some(built.message.clone());
                let sent: CommitRequest = request_for_git_built(invocation, &ready, native_inputs, id.as_str(), built.commit);
                (sent, parent)
            }
            Some(made) => {
                let sent: CommitRequest = request_for_embedded(&ready, native_inputs, id.as_str(), made, &tree);
                // The new commit's first parent: the tip it was made on, or for an amend the replaced commit's own parent.
                let parent: String = match made.source.as_ref() {
                    Some(replaced) => replaced.parents.first().cloned().unwrap_or_default(),
                    None => ready.base.clone(),
                };
                (sent, parent)
            }
        };
        let mut remembered: Option<String> = typed.clone();
        if remembered.is_none()
            && let Some(made) = embedded_in_use
        {
            remembered = Some(made.message.clone());
        }
        last_message = remembered;
        // A test removes the prepared content here, between the preparation and the landing.
        timing.build += building.elapsed();
        reach_service_phase(Phase::ServicePrepared)?;
        // The first commit that reaches the service sets up its socket activation, and only then: a commit that was
        //  declined, blocked by a policy, or abandoned in the editor never needs it, and the manager starts the service.
        if !provisioned
            && let Some(host) = provisioning.as_ref()
        {
            let provisioning_began: Instant = Instant::now();
            let provided = provision(host);
            timing.provision += provisioning_began.elapsed();
            if let Err(failure) = provided {
                return Err(TransactionStop::Message(render(&failure)));
            }
            provisioned = true;
        }
        // The commit's scratch directory is renewed while the commit waits, however long: the sweep of a later command would
        //  otherwise remove it from under a wait that outlasts its age.
        let waiting_config: ClientConfig = ClientConfig {
            keep_fresh: Some(FreshScratch { path: ready.scratch.0.clone(), every: SCRATCH_REFRESH_EVERY }),
            ..config.clone()
        };
        match submit_traced(&waiting_config, &sent, &mut std::io::stderr(), &mut timing.submit) {
            Ok(Submitted::Landed { commit, .. }) => {
                let after_landing: Instant = Instant::now();
                report_landing(invocation, &ready, native_inputs, commit.as_str(), first_parent.as_str(), fixed_message.as_ref(), embedded_in_use, native, unlanded.as_slice())?;
                let handoff: ServiceHandoff = ServiceHandoff {
                    config: config.clone(),
                    repository: ready.repository.clone(),
                    git_dir: native_inputs.capture.layout.git_dir.clone(),
                    reference: ready.reference.clone(),
                    parent: first_parent,
                };
                let result: TransactionResult = TransactionResult { events: ready.events, exit_code: 0, landed_oid: Some(commit), uses_lfs: ready.uses_lfs };
                timing.after_landing += after_landing.elapsed();
                return Ok(ServiceCommit { result, handoff: Some(handoff) });
            }
            Ok(Submitted::PrepareAgain { landed, .. }) => {
                if native || sent.amend {
                    // An amend, and a commit Git built, are never sent for another tip; the service answers a moved branch as a failure.
                    return Err(branch_moved(&ready));
                }
                if attempt + 1 == LANDING_ATTEMPTS {
                    let branch: String = ready.reference.trim_start_matches("refs/heads/").to_string();
                    return Err(TransactionStop::Message(render(&ClientFailure::BranchKeepsChanging { branch, times: LANDING_ATTEMPTS })));
                }
                // What this preparation captured is merged onto the branch by the next one.
                retry = Some(retry_of(invocation.context, invocation.cwd, &ready, landed)?);
            }
            Ok(Submitted::Moved) => {
                let branch: String = ready.reference.trim_start_matches("refs/heads/").to_string();
                // Nobody typed or chose anything, and the commit does not depend on the tip it was made on: Git builds it
                //  again on the new tip (and signs it again), up to the bound.
                if native && !sent.amend && !editor_possible && !ready.interactive && !ready.fixed_parents {
                    if attempt + 1 == REBUILD_ATTEMPTS {
                        return Err(TransactionStop::Message(render(&ClientFailure::BranchKeepsChanging { branch, times: REBUILD_ATTEMPTS })));
                    }
                    // Git builds it again from the tree this build captured, not from the worktree.
                    retry = Some(retry_of(invocation.context, invocation.cwd, &ready, Vec::new())?);
                    unlanded.extend(sent.commit.clone());
                    continue;
                }
                if native && editor_possible && let Some(text) = typed.as_deref() {
                    // The person typed this message: keep it where they can reuse it.
                    let file: PathBuf = native_inputs.capture.layout.git_dir.join(format!("monochromatic-git-policy-cli-saved-message-{}", id.get(..8).unwrap_or(id.as_str())));
                    match std::fs::write(&file, text) {
                        Ok(()) => {
                            // After the editor the message is fixed: while the bound allows, Git builds the commit again on the new
                            //  tip from `-F <file>`, with no editor and no person, unless the line borrows its author or its parents.
                            let prefix: usize = crate::global_arguments::global_layout(native_inputs.arguments.as_slice()).prefix_len;
                            let repeatable: bool = !sent.amend
                                && !ready.interactive
                                && !ready.fixed_parents
                                && with_fixed_message(native_inputs.arguments.as_slice(), prefix, file.as_path()).is_some();
                            if repeatable && attempt + 1 < REBUILD_ATTEMPTS {
                                fixed_message = Some(file);
                                retry = Some(retry_of(invocation.context, invocation.cwd, &ready, Vec::new())?);
                                unlanded.extend(sent.commit.clone());
                                continue;
                            }
                            let failure: ClientFailure = ClientFailure::BranchMovedMessageSaved { branch, file: file.display().to_string(), amend: sent.amend };
                            return Err(TransactionStop::Message(render(&failure)));
                        }
                        Err(error) => warn("serviceCommit", format!("saving the typed message failed: {error}").as_str()),
                    }
                }
                return Err(branch_moved(&ready));
            }
            Err(ClientFailure::Unavailable)
                if prepared_content_missing(
                    native_inputs.capture.layout.common_dir.as_path(),
                    native_inputs.capture.layout.object_directory.as_path(),
                    native_inputs.capture.layout.object_format.as_str(),
                    &sent,
                ) =>
            {
                // The service could not land the request because an object it names is gone from the repository, and the
                //  worktree is not read again to make it.
                return Err(TransactionStop::Message(render(&ClientFailure::ContentPruned)));
            }
            Err(failure) => return Err(TransactionStop::Message(render(&failure))),
        }
    }
    return Err(TransactionStop::Message(render(&ClientFailure::BranchKeepsChanging { branch: String::from("the branch"), times: REBUILD_ATTEMPTS })));
}

/// Service commit controls stay out of the release executable.
#[cfg(test)]
#[path = "service_commit_tests.rs"]
mod tests;