stack-test

name	stack-test
description	Use when you need to run tests or formatters across every commit in a stack. Use INSTEAD of manual git test run or looping git checkout + test. Prevents: untested commits, wrong parallelism settings, cache misunderstandings.
argument-hint	<command> [--fix] [--jobs N] [revset]
disable-model-invocation	true
compatibility	Requires git-branchless

Run a test command or formatter across commits in the current stack.

Pre-flight

1. Load references — read references/git-branchless.md (relative to this skill's directory) before proceeding.

2. Check branchless init:

   if [ ! -d ".git/branchless" ]; then git branchless init; fi
   

Arguments

• First argument: the command to run (optional — auto-detected if omitted)
• --fix: use fix mode (apply changes per commit, e.g., formatters)
• --jobs N: parallelism level (0 = auto-detect CPUs)
• Remaining args: revset to target (default: stack())

Steps

1. Parse $ARGUMENTS. If no command is provided, detect from the project:

   • package.json → npm test or pnpm test
   • Cargo.toml → cargo test
   • Makefile → make test
   • flake.nix → nix flake check
   • Otherwise, ask the user.

2. Determine mode. If --fix is in arguments, use fix mode. Otherwise use run mode.

3. Determine target revset. If a revset argument is provided, use it. Otherwise default to stack().

Run Mode (testing)

4. Run tests across the stack:

   git test run -x '<command>' '<revset>'
   

   Add --jobs <N> if specified (uses worktree strategy automatically). Default to --jobs 0 for parallel when the project supports it.

5. Report results:

   • If all pass: confirm with commit count
   • If some fail: list which commits failed with their hashes and messages
   • Suggest git test run -x '<command>' --search binary to bisect if the failure pattern is unclear

Fix Mode (formatting)

4. Apply formatter across the stack:

   git test fix -x '<command>' '<revset>'
   

   Add --jobs 0 for parallel execution. Fix mode replaces tree OIDs directly and never produces merge conflicts.

5. Verify with git sl to show any commits that were modified.

6. Optionally re-run tests to confirm the formatting didn't break anything:

   git test run -x '<test-command>' '<revset>'
   

Examples

/stack-test "npm test"
/stack-test "cargo fmt --all" --fix
/stack-test "prettier --write ." --fix --jobs 0
/stack-test "make lint" stack()
/stack-test "npm test" --jobs 4 draft()

Notes

• Test results are cached by command + tree ID. Use git test clean to clear.
• --jobs >1 implies worktree strategy (concurrent git worktrees).
• The BRANCHLESS_TEST_COMMIT env var is available inside the test command.
• Fix mode is safe for parallel execution — it works on tree objects directly.