Retrieve Diff from Commit Skill

An input skill that retrieves code diff from local git commits. This is the entry point for reviewing local changes before they are pushed.

Role

Extract: Get the diff content from a specific commit or range of commits
Format: Prepare the diff in a format suitable for code review
Context: Gather commit metadata (author, message, timestamp)

Inputs

Input	Required	Description
`commit_sha`	Optional	Specific commit SHA to review (defaults to HEAD)
`commit_range`	Optional	Range of commits (e.g., `main..HEAD`, `HEAD~3..HEAD`)
`base_branch`	Optional	Compare current branch against base (e.g., `main`, `develop`)

Outputs

Output	Description
`diff`	The unified diff content
`files_changed`	List of files modified with change type (added/modified/deleted)
`commit_info`	Commit metadata (SHA, author, message, timestamp)
`stats`	Summary statistics (lines added, deleted, files changed)

Usage

Review Single Commit

# Get diff for specific commit
git show <commit_sha> --format="%H%n%an%n%ae%n%s%n%b" --stat

# Get unified diff
git diff <commit_sha>^..<commit_sha>

Review Commit Range

# Get diff for range
git diff <base_commit>..<head_commit>

# Get list of commits in range
git log --oneline <base_commit>..<head_commit>

Review Branch Against Base

# Compare feature branch to main
git diff main...HEAD

# Get merge-base
git merge-base main HEAD

Step 1: Identify the Scope

Determine what to review:

Scenario	Command	Use Case
Last commit	`git diff HEAD~1..HEAD`	Quick review of latest change
All uncommitted	`git diff`	Review before committing
Staged changes	`git diff --cached`	Review what will be committed
Branch diff	`git diff main...HEAD`	Full feature review
Specific commit	`git show <sha>`	Review single commit

Step 2: Extract Diff

Execute the appropriate git command:

# For comprehensive diff with context
git diff --unified=5 <base>..<head>

# Include file stats
git diff --stat <base>..<head>

# Get list of changed files
git diff --name-status <base>..<head>

Step 3: Gather Metadata

Collect commit information:

# Get commit details
git log --format="%H|%an|%ae|%at|%s" <base>..<head>

# Get file change summary
git diff --shortstat <base>..<head>

Step 4: Format Output

Structure the output for the review pipeline:

## Diff Retrieved

**Commit Range**: `<base>..<head>`
**Files Changed**: X
**Lines Added**: +Y
**Lines Deleted**: -Z

### Files

| Status | File |
|--------|------|
| M | src/auth/login.ts |
| A | src/utils/helper.ts |
| D | src/deprecated.ts |

### Diff Content

\`\`\`diff
<unified diff content>
\`\`\`

### Commit Info

| Field | Value |
|-------|-------|
| SHA | abc123... |
| Author | John Doe <john@example.com> |
| Date | 2024-01-15 10:30:00 |
| Message | feat: add login functionality |

Output Format

{
  "source": "local-git",
  "commit_range": {
    "base": "<base_sha>",
    "head": "<head_sha>"
  },
  "stats": {
    "files_changed": 5,
    "insertions": 120,
    "deletions": 45
  },
  "files": [
    {
      "path": "src/auth/login.ts",
      "status": "modified",
      "additions": 50,
      "deletions": 10
    }
  ],
  "commits": [
    {
      "sha": "abc123",
      "author": "John Doe",
      "email": "john@example.com",
      "timestamp": "2024-01-15T10:30:00Z",
      "message": "feat: add login functionality"
    }
  ],
  "diff": "<unified diff content>"
}

Integration with Review Pipeline

After retrieving the diff, pass the output to:

codereview-orchestrator - For triage and routing
Then to appropriate specialist skills based on the triage

Quick Reference

□ Identify Scope
  □ Single commit, range, or branch?
  □ Committed or uncommitted?

□ Extract Diff
  □ Run appropriate git diff command
  □ Include sufficient context (--unified=5)

□ Gather Metadata
  □ Commit info (SHA, author, message)
  □ File statistics

□ Format Output
  □ Structure for review pipeline
  □ Include all necessary context

Example Usage in Pipeline

1. retrieve-diff-from-commit (this skill)
   ↓
2. codereview-orchestrator (triage)
   ↓
3. Specialist skills (review)
   ↓
4. Output formatted findings