Git Version Control

<skill_scope skill="git-version-control"> Related skills:

• software-engineer — Design principles that inform commit granularity
• test-driven-development — Test-commit cycles and when to commit during TDD

This skill covers Git commit standards, branch strategy, and LLM-assisted development workflows. It emphasizes atomic commits, meaningful commit messages, and high-frequency integration. </skill_scope>

Core Philosophy

<core_philosophy> "Commit Often, Perfect Later, Publish Once" — Seth Robertson

Integration frequency is the most powerful determinant of branching success. Elite teams integrate multiple times daily. "If it hurts, do it more often." — Martin Fowler

Revertability principle: Commits should represent meaningful units of work that could be reverted independently without breaking the system. </core_philosophy>

Commit Practices

<atomic_commits> Atomic commit decision: "If you can describe what you did in a short sentence and it makes sense, commit."

When larger commits are acceptable: Initial prototyping (squash before review), closely coupled changes, when over-granularity loses context.

Time guideline: 30-60 min ideal, max 4 hours. See <commit_triggers> for event-based commit points. </atomic_commits>

Commit Triggers

<commit_triggers> Commits are responses to completion events, not scheduled activities.

Commit discipline isn't about remembering to commit—it's about recognizing completion signals.

<observable_completion_events> #### Observable Completion Events

Key insight: Passing tests/builds are commit signals, not just validation. Green means save your progress. </observable_completion_events>

<transition_points> #### Transition Points

</transition_points>

<conversational_cues> #### LLM-Assisted Conversational Cues

In LLM-assisted development, user messages signal completion:

Anti-pattern: Batching multiple unrelated changes because "I'll commit later." Each completion event deserves its own commit. </conversational_cues> </commit_triggers>

Branch Discipline

<branch_discipline> Before committing, verify you're on the appropriate branch:

LLM-assisted pattern: When starting work that might need multiple commits, proactively create a feature branch before the first commit. Ask the user if uncertain about scope.

<merge_strategy> Merge strategy for completed branches:

Squash preference: Feature branches with more than 3-5 commits should generally be squash-merged. The intermediate commits represent implementation exploration, not meaningful history. Mainline should tell the story of what changed, not how you figured it out. </merge_strategy> </branch_discipline>

<conventional_commits> Style preference: Use full keywords (feature: not feat:). Imperative mood. Subject ≤50 chars, body wraps at 72, explain WHY.

Imperative mood test: Subject line should complete the sentence "If applied, this commit will _____."[^beams] Examples: "Add caching for API responses" ✓, "Added caching" ✗, "Adds caching" ✗.

Content principles:

• Delta, not journey — Describe what changed, not how you discovered what to change. The debugging process doesn't belong in the permanent record.
• Neutral framing — Avoid judgmental language about prior state ("fix broken", "remove wrong", "correct mistake"). Prefer neutral verbs: "update", "change", "revise".
• Outcome, not process — Don't document how you verified, tested, or arrived at the change. The commit message records what, not how you figured it out.
• Let the diff speak — Implementation details belong in the diff. The message explains intent and scope; the diff shows specifics.

Anti-pattern: "Fix incorrect attribution that cited Apple docs when the quote was actually from a community blog post" — this documents the debugging journey, uses judgmental framing, and includes detail the diff already shows.

Better: "Update source attributions" — neutral, outcome-focused, appropriate abstraction level. </conventional_commits>

<fixup_workflow>

git commit --fixup=<sha>           # Creates "fixup! Original message"
git rebase --autosquash origin/main # Squashes fixups automatically
git config --global rebase.autosquash true

</fixup_workflow>

Branching Strategies

<branching_decision>

Trunk-based: Short-lived branches (<24h), feature flags for incomplete work.

Branch naming: <category>/<ticket-id>-<description> (e.g., feature/PROJ-4521-add-oauth) </branching_decision>

<merge_vs_rebase> Rebase: Private branches, linear history, working alone. Merge: Public/shared branches, preserve collaboration history, audit trails.

GOLDEN RULE: Never rebase commits others may have based work on.

Force push safety: After rebasing a personal branch, use --force-with-lease instead of --force. It fails if someone else pushed, preventing you from overwriting their work.

git push --force-with-lease  # Safe
git push --force             # Dangerous

CRITICAL: NEVER force push to main/master branches. Even with --force-with-lease, force pushing to primary branches can destroy team history, break CI/CD pipelines, and cause widespread disruption. If this is ever requested, warn about the consequences first. </merge_vs_rebase>

<interactive_limitations> LLM-assisted context limitation: Interactive git commands (git rebase -i, git add -i, git add -p) require terminal interaction and are unavailable in LLM-assisted contexts. Use alternatives:

• Instead of git rebase -i: Use --autosquash with fixup commits
• Instead of git add -i: Use explicit git add <file> commands
• Instead of git add -p: Stage specific files, or use GUI tools

</interactive_limitations>

LLM-Assisted Development Patterns

Checkpoint Commits

<llm_checkpoints> Lightweight savepoints before LLM modifications without commit overhead.

Git aliases (adapted from Nathan Orick's checkpoint pattern[^orick]):

[alias]
checkpoint = "!f() { git add -A && git commit --no-verify -m \"SAVEPOINT\"; git tag \"checkpoint/$(date +%Y_%m_%d_%H_%M_%S)\"; git reset HEAD~1 --mixed; }; f"
listCheckpoints = tag -l "checkpoint/*"
loadCheckpoint = "!f() { git reset --hard checkpoint/$1 && git reset HEAD~1 --mixed; }; f"
deleteCheckpoint = "!f() { git tag -d checkpoint/$1; }; f"

Workflow:

git checkpoint                              # Before LLM changes
git listCheckpoints                         # View savepoints
git loadCheckpoint 2024_11_15_13_25_55      # Restore if bad

</llm_checkpoints>

Commit Frequency by Context

<commit_frequency>

</commit_frequency>

Generate-Test-Commit-or-Revert

<generate_test_commit>

1. CHECKPOINT before LLM generates code
2. TEST — run tests, build, verify
3. DECIDE — pass → commit immediately; fail → restore checkpoint
4. REVIEW — PR before merge

Key insight: AI excels at generating plausible-looking but subtly incorrect code. Time saved by being careless will dwarf the mess you'll face later.

If LLM fails 3+ times, break it down further — abstraction level too high. </generate_test_commit>

Context Management

<context_management>

git diff --no-pager --no-color HEAD^  # Full diff for review
git diff -U0                          # No context (fewer tokens)
git diff --cached                     # Staged changes only

</context_management>

Recovery Patterns

<recovery_triggers> Reflog — Recover from rebases, resets, amends. Local only, 90 days default.

git reflog
git reset --hard HEAD@{5}
git reset --hard main@{2.hours.ago}

Rerere — Auto-resolve repeated conflicts. Enable: git config --global rerere.enabled true

Bisect — O(log n) regression hunting.

git bisect start && git bisect bad HEAD && git bisect good v1.0
git bisect run make test  # Automated

</recovery_triggers>

Tool Selection

<stash_branch_worktree>

Multi-agent worktrees:

git worktree add ../agent-1-workspace feature-auth
git worktree add ../agent-2-workspace feature-payment

</stash_branch_worktree>

Anti-Patterns

<anti_patterns> Commit Anti-Patterns:

• Broken code on main: Every commit on main should pass tests and build. Use feature branches or feature flags.
• Giant mixed-concern commits: Mixing refactoring with features makes review and revert impossible. Separate concerns.
• Meaningless messages: "fix", "update", "WIP" provide no context. Explain WHY, not just WHAT.
• Committing secrets: API keys, credentials, private keys. Use .gitignore, git-secrets, or pre-commit hooks.

Branch Anti-Patterns:

• Long-lived branches (>1 week): Merge conflicts compound exponentially. Integrate frequently.
• Rebasing public branches: Rewrites shared history. Use merge for shared branches.
• No feature flags on trunk: Incomplete features on main without flags block releases.
• Force pushing to main/master: Destroys team history. Never do this.

LLM-Assisted Anti-Patterns:

• "Vibe coding" without review: LLM output requires human verification before commit.
• No checkpoints before LLM changes: Always checkpoint before LLM modifications for easy rollback.
• Context drift from large windows: Long conversations lose context. Break into smaller tasks.

</anti_patterns>

Common Mistakes by Background

<common_mistakes>

From SVN/Perforce Users

• Treating branches as expensive (they're cheap in Git—use them freely)
• Expecting central locking (Git is distributed—conflicts resolve at merge)
• Not pulling before push (always git pull --rebase before pushing)
• Expecting linear history without effort (requires disciplined rebasing)

From Solo Developers

• Not considering rebase vs merge implications (matters when collaborating)
• Treating main as scratch space (use feature branches even when solo)
• Giant commits because "only I use this" (future you will regret it)
• No commit message discipline (you'll forget why in 6 months)

From GUI-Only Users

• Not understanding what commands the GUI executes (learn the underlying operations)
• Panic when something goes wrong (reflog saves almost everything)
• Not leveraging command-line power for scripting and automation

</common_mistakes>

Resources

<resources> Official:

• Git Documentation
• Pro Git Book

Patterns:

• Martin Fowler: Branching Patterns
• ConventionalCommits.org
• Nathan Orick: Git Checkpoints

</resources>

Sources

<sources> [^beams]: Chris Beams. 2014. How to Write a Git Commit Message. https://cbea.ms/git-commit/

[^orick]: Nathan Orick. Git Checkpoints. https://nathanorick.com/git-checkpoints/ </sources>