refactor(stack): extract shared git helpers into crate::git

[jd]

Every per-command stack module (drop, fixup, reword, reorder,
move, squash, checkout, sync, list, note, edit, setup, new, push)
maintained its own slight variant of shell_quote,
resolve_repo_toplevel, spawn_rebase, run_git_capture, and
run_git_silent. Three of the newer leaf modules
(change_type, notes_push, replay) additionally set
LC_ALL=C/LANG=C/LANGUAGE=C because they parse English git error
messages; the per-command duplicates didn't, which would have
been a flake waiting to happen on non-English systems.

Consolidate into crates/mergify-stack/src/git.rs:

• git_cmd(repo_dir) — base Command with -C <dir> (when
  supplied) and the forced C locale.
• run_git_capture(repo_dir, args) — trimmed stdout or
  CliError::Generic with the captured stderr.
• run_git_silent(repo_dir, args) — same error mapping,
  output discarded.
• resolve_repo_toplevel(repo_dir) — git rev-parse --show-toplevel as a PathBuf.
• spawn_rebase(repo_dir, base, sequence_editor) — interactive
  rebase with the optional GIT_SEQUENCE_EDITOR env (the
  None arm is what stack edit's "fall through to the user's
  editor" path used).
• shell_quote(value) — POSIX shell single-quote escape.

Every consumer module updated to import from crate::git; the
duplicated function bodies (~50-100 lines per module) deleted.
Side effects:

• The previously locale-unaware per-command helpers now force
  LC_ALL=C like the leaf modules already did. Downstream call
  sites that match git error messages by English substring
  (couldn't find remote ref, etc.) now work consistently across
  locales — a latent bug fix.
• Call-site signature updates: spawn_rebase now takes
  Option<&str> for the editor (was &str in most consumers,
  Option<&str> in edit); commands::sync's run_git /
  spawn_rebase_with_editor got renamed to the shared
  run_git_silent / spawn_rebase; commands::push's
  run_git_silent signature changed from &Path to
  Option<&Path>.

Addresses Copilot's review feedback on PR #1518 (stack fixup)
about helper duplication across drop/edit/fixup/... — the
extraction unifies all 13 consumer modules in one commit.

All 241 mergify-stack tests + the rest of the workspace pass.

Co-Authored-By: Claude Opus 4.7 noreply@anthropic.com

Depends-On: #1554

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	feat(rust): port stack checkout to native Rust	#1522
2	feat(rust): port stack sync to native Rust	#1523
3	feat(rust): port stack list + stack open to native Rust	#1524
4	feat(rust): port stack hooks + stack setup to native Rust	#1527
5	feat(rust): port stack push end-to-end + delete Python push.py	#1553
6	chore: delete Python tree + simplify wheel/CI for pure-Rust binary	#1554
7	refactor(stack): extract shared git helpers into crate::git	#1555	👈
8	ci(workflows): align smoke-test-binary on python 3.14	#1557

[mergify]

Merge Protections

Your pull request matches the following merge protections and will not be merged until they are valid.

🔴 ⛓️ Depends-On Requirements

Waiting for

• depends-on=Mergifyio/mergify-cli#1522 [⛓️ feat(rust): port stack checkout to native Rust #1522 [stack]]
• depends-on=Mergifyio/mergify-cli#1523 [⛓️ feat(rust): port stack sync to native Rust #1523 [stack]]
• depends-on=Mergifyio/mergify-cli#1524 [⛓️ feat(rust): port stack list + stack open to native Rust #1524 [stack]]
• depends-on=Mergifyio/mergify-cli#1527 [⛓️ feat(rust): port stack hooks + stack setup to native Rust #1527 [stack]]
• depends-on=Mergifyio/mergify-cli#1553 [⛓️ feat(rust): port stack push end-to-end + delete Python push.py #1553 [stack]]
• depends-on=Mergifyio/mergify-cli#1554 [⛓️ chore: delete Python tree + simplify wheel/CI for pure-Rust binary #1554 [stack]]

This rule is failing.

Requirement based on the presence of Depends-On in the body of the pull request

• depends-on=Mergifyio/mergify-cli#1522 [⛓️ feat(rust): port stack checkout to native Rust #1522 [stack]]
• depends-on=Mergifyio/mergify-cli#1523 [⛓️ feat(rust): port stack sync to native Rust #1523 [stack]]
• depends-on=Mergifyio/mergify-cli#1524 [⛓️ feat(rust): port stack list + stack open to native Rust #1524 [stack]]
• depends-on=Mergifyio/mergify-cli#1527 [⛓️ feat(rust): port stack hooks + stack setup to native Rust #1527 [stack]]
• depends-on=Mergifyio/mergify-cli#1553 [⛓️ feat(rust): port stack push end-to-end + delete Python push.py #1553 [stack]]
• depends-on=Mergifyio/mergify-cli#1554 [⛓️ chore: delete Python tree + simplify wheel/CI for pure-Rust binary #1554 [stack]]

🔴 👀 Review Requirements

Waiting for

• #approved-reviews-by>=2

This rule is failing.

• any of:
  • #approved-reviews-by>=2
  • author = dependabot[bot]
  • author = mergify-ci-bot
  • author = renovate[bot]

🔴 🔎 Reviews

Waiting for

• #review-requested = 0

This rule is failing.

• #review-requested = 0
• #changes-requested-reviews-by = 0
• #review-threads-unresolved = 0

🟢 🤖 Continuous Integration

Wonderful, this rule succeeded.

• all of:
  • check-success=ci-gate

🟢 Enforce conventional commit

Wonderful, this rule succeeded.

Make sure that we follow https://www.conventionalcommits.org/en/v1.0.0/

• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert|ui)(?:\(.+\))?:

🟢 📕 PR description

Wonderful, this rule succeeded.

• body ~= (?ms:.{48,})

[jd]

Revision history

#	Type	Changes	Reason	Date
1	initial	df83c39		2026-06-05 09:38 UTC
2	rebase	df83c39 → 2dd5d91 (rebase only)		2026-06-05 09:38 UTC
3	rebase	2dd5d91 → faf159c (rebase only)		2026-06-05 11:15 UTC
4	rebase	faf159c → f4d2fe7 (rebase only)		2026-06-05 12:37 UTC
5	rebase	f4d2fe7 → c5f353a (rebase only)		2026-06-08 11:31 UTC
6	rebase	c5f353a → 49231a6 (rebase only)		2026-06-08 15:03 UTC