git-analysis

name	git-analysis
description	Analyze git repository changes, branch differences, and commit history. Use when analyzing branches, comparing changes, examining commit history, or preparing for PR/commit operations.

Git Analysis

This Skill provides comprehensive git repository analysis capabilities for understanding branch changes, commit history, and code differences.

Capabilities

• Analyze branch differences and merge bases
• Extract structured commit history
• Identify changed files and their statistics
• Determine default branches and remote configuration
• Support PR creation, code review, and commit operations

When to Use

Use this Skill when you need to:

• Analyze what changed in a branch
• Prepare information for PR creation
• Review commit history
• Compare branches
• Understand code changes for commits or reviews

Core Analysis Steps

1. Identify Default Branch

Get the repository's default branch (usually main or master):

git symbolic-ref refs/remotes/origin/HEAD | sed 's@^refs/remotes/origin/@@'

This identifies the base branch for comparison.

2. Find Merge Base

Determine where the current branch diverged from the default branch:

# Get merge base
git merge-base origin/<default-branch> HEAD

The merge base is the commit where the branch diverged, not the current state of the base branch.

3. Analyze Changes

Get comprehensive change information:

# List commits from merge base
git log --oneline <merge-base>..HEAD

# Get detailed commit information
git log --format="%H|%s|%an|%ae|%ad" --date=iso <merge-base>..HEAD

# Get file statistics
git diff --stat <merge-base>..HEAD

# Get full diff
git diff <merge-base>..HEAD

4. Check Current State

Understand unstaged and staged changes:

# Check untracked files
git status

# Check staged changes
git diff --cached

# Check unstaged changes
git diff

Helper Scripts

This Skill includes helper scripts for common operations:

get_branch_diff.sh

Extracts branch differences including:

• Default branch name
• Merge base commit
• Commit list with statistics
• Changed files summary

Usage:

bash scripts/get_branch_diff.sh

Output format:

DEFAULT_BRANCH: main
MERGE_BASE: abc123def456
COMMITS: 5
CHANGED_FILES: 12

get_commit_history.sh

Extracts detailed commit history in structured format:

Usage:

bash scripts/get_commit_history.sh <merge-base>

Output format (one commit per line):

hash|subject|author_name|author_email|date

Best Practices

1. Always use merge-base: Compare from merge base, not from current base branch state
2. Run commands in parallel: When gathering multiple pieces of information, run independent git commands in parallel
3. Structure the output: Parse git output into structured data for easier consumption
4. Handle errors gracefully: Check if commands succeed before proceeding

Common Patterns

Pattern 1: Full Branch Analysis

# Get all information in parallel
git status &
git diff --cached &
git diff &
DEFAULT_BRANCH=$(git symbolic-ref refs/remotes/origin/HEAD | sed 's@^refs/remotes/origin/@@')
MERGE_BASE=$(git merge-base origin/$DEFAULT_BRANCH HEAD)
git log --oneline $MERGE_BASE..HEAD
git diff --stat $MERGE_BASE..HEAD
wait

Pattern 2: Commit History Extraction

# Get structured commit data
MERGE_BASE=$(git merge-base origin/$(git symbolic-ref refs/remotes/origin/HEAD | sed 's@^refs/remotes/origin/@@') HEAD)
git log --format="%H|%s|%an|%ae|%ad" --date=iso $MERGE_BASE..HEAD

Pattern 3: Change Summary

# Get high-level change summary
MERGE_BASE=$(git merge-base origin/$(git symbolic-ref refs/remotes/origin/HEAD | sed 's@^refs/remotes/origin/@@') HEAD)
echo "Commits: $(git log --oneline $MERGE_BASE..HEAD | wc -l)"
echo "Files changed: $(git diff --stat $MERGE_BASE..HEAD | tail -1)"

Integration with Other Skills

This Skill works well with:

• github-pr-best-practices: Use git analysis results to generate PR content
• Commit message generation: Analyze changes to create meaningful commit messages
• Code review: Understand what changed for review purposes

Error Handling

Handle common git errors:

# Check if in git repository
if ! git rev-parse --git-dir > /dev/null 2>&1; then
    echo "Error: Not in a git repository"
    exit 1
fi

# Check if remote exists
if ! git ls-remote origin > /dev/null 2>&1; then
    echo "Error: Remote 'origin' not found"
    exit 1
fi

# Check if branch has commits
if [ -z "$(git log --oneline $MERGE_BASE..HEAD)" ]; then
    echo "Warning: No commits found in branch"
fi

Output Format Recommendations

When presenting git analysis results:

1. Summary first: Start with high-level statistics
2. Structured data: Use consistent formatting for easy parsing
3. Contextual information: Include branch names and dates
4. Actionable insights: Highlight what's important for the task

Example output structure:

Branch Analysis Summary
-----------------------
Base branch: main
Current branch: feature/new-feature
Diverged at: abc123d (2025-01-15)

Changes:
- 5 commits
- 12 files changed
- 234 insertions, 89 deletions

Recent commits:
1. feat(api): add new endpoint (2025-01-16)
2. test(api): add endpoint tests (2025-01-16)
3. docs(api): update API documentation (2025-01-17)
...

Related Git Commands Reference

See REFERENCE.md for detailed git command documentation and advanced usage patterns.