split-commit

name	split-commit
description	Repackage branch into clean, tested, vertical commits. Triggers: 'split commits', 'repackage commits', 'reorganize commits', 'clean up branch history'. Not for single-commit branches — use /commit instead.
argument-hint	[base-branch] [--test='command'] [--auto]
user-invocable	true
allowed-tools	["Bash"]

Split Commit

Repackage branch changes into clean vertical commits. Each commit compiles + passes tests independently.

Phase 1: Analyze

Parse: <base-branch>, optional --test='command'. If no base-branch arg, resolve at runtime: gh stack view --json 2>/dev/null | jq -r '.trunk // empty' || gt parent 2>/dev/null || gt trunk 2>/dev/null || git symbolic-ref refs/remotes/origin/HEAD 2>/dev/null | sed 's|refs/remotes/||'.

Noop check — git log --oneline <base>..HEAD | wc -l. If ≤1 → stop: "Nothing to repackage — use /commit."

Dispatch analysis subagent (general-purpose):

Analyze changes for repackaging into clean vertical commits.
Base branch: <base-branch>

Steps:
1. `git log --oneline <base>..HEAD | wc -l` + `git diff --stat <base>..HEAD | tail -40`
2. Full diff: `git diff <base>..HEAD` — Explore subagent for large diffs
3. Trace cross-file deps, group vertically, order: foundational → features → cleanup
4. For shared files, note which hunks belong where

Auto-detect test commands from justfile/Makefile/package.json/Cargo.toml. Use --test if provided.

Cross-file dep rules:
- File A imports B → same commit or B earlier
- Config/lock files go with the feature introducing the dep
- New types/interfaces go with first consumer

Output:
TEST_COMMANDS: <detected or provided>
COMMIT_PLAN:
1. `type(scope): message` — Files: <list>, Partial: <hunks>, Deps: <justification>, Rationale: <why>
DEPENDENCY_NOTES: <hunk splitting, ordering constraints>

--auto → proceed directly. Otherwise → present plan via AskUserQuestion: commit count, test commands, each commit + key files. "Proceed?"

Phase 2: Execute

Collapse into unstaged changes:

git reset --soft <base> && git reset HEAD

Dispatch a single execution subagent (model="sonnet") for ALL commits:

Create <total> commits from unstaged changes.
Commit plan: <full plan from analysis>
Test commands: <test-commands>

Per commit:
1. `git-surgeon hunks` — list available hunks
2. Stage target hunks: whole files → all hunks; partial → `git-surgeon show <id>`, stage matching
3. Run tests. FAIL → find missing dep, stage, retry once. Still failing → STOP with commit number + error.
4. `git commit -m "<message>"`

After last commit: `git diff --stat` — report remaining unstaged.

On failure: spawn fix subagent, then re-invoke execution subagent for remaining commits only.

Verify after all commits:

git status          # should be clean
git log --oneline <base>..HEAD   # N clean commits

Dirty tree → cleanup subagent: stage remaining, test, commit as chore: clean up remaining. Still fails → report.

Key Rules

• No tasks — pure git operation, one-shot
• Two subagents — analysis + execution (fix subagent only on failure)
• git-surgeon always — hunk-level precision for partial file staging
• Every commit compiles — broken history is worse than plan deviation
• Plan > rigidity — test failures from missing deps override grouping