git-post-merge-cleanup git:20260905.a73d7eaA

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---
name: git-post-merge-cleanup
description: >-
  Rules, safety constraints, and automated procedures for post-merge local Git cleanup,
  synchronizing main with GitHub, deleting stale local branches, and performing deep
  repository garbage collection (git gc, reflog expire, prune) strictly upon explicit human user request.
---

# Git Post-Merge Repository & Branch Cleanup Skill

This skill defines the official protocol and step-by-step procedures for cleaning up local development branches, pulling the latest `main` from GitHub after a Pull Request is merged, and executing deep Git repository garbage collection and maintenance.

---

## 1. Strict Permission & Trigger Boundary

> [!IMPORTANT]
> **EXPLICIT HUMAN INSTRUCTION ONLY**:
> AI agents MUST NEVER run local branch deletions, branch resets, or aggressive garbage collection automatically.
> This workflow is triggered **ONLY** when the human user explicitly instructs the agent to perform cleanup (e.g. *"clean up local branches"*, *"sync main and do git gc"*, *"I merged the PR, please clean up"*).
>
> The typical workflow is:
> 1. AI agent finishes work on a feature branch, passes pre-commit checks, commits locally, pushes branch, and opens a PR targeting `main`.
> 2. The human user reviews and merges the Pull Request on GitHub.
> 3. The human user prompts the AI agent to perform local cleanup.
> 4. The AI agent executes the safe post-merge cleanup runbook below.

---

## 2. Core Cleanup Principles

1. **Safety-First Working Tree Verification**: Never switch branches or run destructive cleanups if there are uncommitted changes or uncommitted work in progress.
2. **Main as the Source of Truth**: Always switch to `main` and pull from `origin/main` first so that the newly merged PR code and history are fully present locally before deleting the feature branch.
3. **Preserve `main` (and Protected Branches)**: Only delete feature/task branches. Never delete `main`.
4. **Remote Reference Pruning**: Prune stale remote tracking branches (`git fetch --prune origin`) to keep the remote tracking tree clean.
5. **Deep Garbage Collection**: Prune unreachable reflog entries (`git reflog expire --expire=now --all`) and optimize the local object store (`git gc --prune=now --aggressive`) to keep the `.git` directory small, fast, and healthy.
6. **Zero Stale Branches**: After cleanup, only `main` remains as the active local branch.

---

## 3. Step-by-Step Cleanup Runbook

When the human user requests post-merge cleanup, execute these exact steps in sequence:

### Step 1: Verify Working Directory State
Ensure there are no unstaged modifications or stash conflicts:
```bash
git status
```
If dirty, stop and check if there are uncommitted files that need to be preserved.

### Step 2: Switch to `main` and Pull Latest Upstream
Switch to the primary release branch and pull the merged changes from GitHub:
```bash
git switch main
git pull origin main
```

### Step 3: Prune Remote Tracking Branches
Synchronize and remove remote branch references that were deleted on GitHub after PR merge:
```bash
git fetch --prune origin
```

### Step 4: Identify & Delete Local Feature Branches
List all local branches to inspect what needs to be removed:
```bash
git branch
```
Delete all local feature branches (e.g. `<github-username>/main/<feature>`):
```bash
# Safe delete merged branches:
git branch -d <branch-name>

# If GitHub used Squash & Merge or Rebase & Merge (which changes commit hashes):
git branch -D <branch-name>
```

Or delete all local branches except `main` in one command:
```bash
git branch | grep -v "^\* main$" | grep -v "^  main$" | xargs -r git branch -D
```

### Step 5: Expire Reflogs & Run Aggressive Garbage Collection
Clean up dangling commits, unreachable objects, and optimize packfiles:
```bash
git reflog expire --expire=now --all
git gc --prune=now --aggressive
```

### Step 6: Verify Final Repository State
Verify that only `main` remains and the working tree is clean:
```bash
git branch
git status
```

---

## 4. Automated Remote Branch Cleanup on PR Merge

Remote feature branch deletion can be automated via GitHub Actions:
- **Trigger**: Triggers automatically on `pull_request: [closed]` when `merged == true`.
- **Action**: Deletes the remote feature branch on GitHub, preventing stale remote reference buildup.