git-blame-reviewer

A Git tool that mimics the behavior of git blame but shows GitHub pull request or GitLab merge request approvers for each line of code instead of the original commit authors.

Inspired by @CubicleApril:

Features

• 🔍 Shows who approved the changes for each line of code
• ⏰ Displays approval timestamps instead of commit timestamps
• 📋 Identical interface to git blame - same command-line arguments and output format
• 🎨 Supports both human-readable and porcelain output formats
• 🚀 Built with Go - single binary, no external dependencies
• ⚡ Optimized with commit-level caching to minimize API calls
• 🌐 Supports both GitHub and GitLab - automatically detects repository type
• 🏢 Works with self-hosted GitLab instances

Installation

From Source

git clone <repository-url>
cd git-blame-reviewer
make build

Binary

The compiled binary will be available as git-blame-reviewer.

Usage

git-blame-reviewer uses the exact same command-line interface as git blame:

Basic Usage

git-blame-reviewer src/main.go

With Line Range

git-blame-reviewer -L 10,20 src/main.go

Porcelain Format (Machine-Readable)

git-blame-reviewer -porcelain src/main.go

Show Email Addresses

git-blame-reviewer -show-email src/main.go

Command Line Options

• -L <start>,<end> - Show only lines in given range (same as git blame)
• -porcelain - Show in a format designed for machine consumption
• -show-email - Show author email instead of author name
• -help - Show help message

Note: The file path is provided as a positional argument, just like git blame.

API Tokens

GitHub Token

You'll need a GitHub personal access token with repo scope to access pull request information.

1. Go to GitHub Settings > Developer settings > Personal access tokens
2. Generate new token with repo scope

GitLab Token

You'll need a GitLab personal access token with read_api and read_repository scopes.

1. Go to GitLab Settings > Access Tokens
2. Generate new token with read_api and read_repository scopes

Usage:

GitHub Repositories

export GITHUB_TOKEN=ghp_xxxxxxxxxxxx
git-blame-reviewer src/main.go

GitLab Repositories

export GITLAB_TOKEN=glpat_xxxxxxxxxxxx
git-blame-reviewer src/main.go

Self-hosted GitLab

export GITLAB_TOKEN=glpat_xxxxxxxxxxxx
git-blame-reviewer src/main.go  # Works automatically with self-hosted instances

The tool automatically detects whether your repository is hosted on GitHub or GitLab based on the remote origin URL and uses the appropriate token.

Development

Prerequisites

• Go 1.25.1+
• Make
• golangci-lint (install with make install-tools)

Building

make build

Testing

make test
make test-coverage  # with coverage report

Linting

make lint

All Checks

make check  # runs tests + linting

How It Works

1. Git Repository Detection - Finds the git repository root and validates it's a git directory
2. Repository Type Detection - Automatically detects GitHub vs GitLab from remote origin URL
3. Repository Info Extraction - Extracts owner/repository name from git remote origin
4. Git Blame Execution - Runs git blame on the specified file to get commit hashes per line
5. API Integration - For each unique commit hash:
   • GitHub: Queries GitHub API to find associated pull request and approvals
   • GitLab: Queries GitLab API to find associated merge request and approvals
   • Caches results to avoid duplicate API calls
6. Output Formatting - Displays results in the same format as git blame, but with:
   • PR/MR approver name instead of commit author
   • PR/MR approval timestamp instead of commit timestamp
   • Falls back to original commit info if no PR/MR/approval found

Output Format

The output format is identical to git blame:

a1b2c3d4 (Jane Smith    2023-12-01 14:30:25  1) package main
b2c3d4e5 (Bob Wilson    2023-12-01 09:15:10  2) 
c3d4e5f6 (Alice Johnson 2023-11-30 16:45:30  3) import "fmt"

Where:

• a1b2c3d4 - Commit hash (shortened)
• Jane Smith - PR/MR approver name (not commit author)
• 2023-12-01 14:30:25 - PR/MR approval timestamp (not commit timestamp)
• 1 - Line number
• package main - Line content

Supported Platforms

Platform	URL Format	Token Type	Scope Required
GitHub.com	github.com/owner/repo	Personal Access Token	repo
GitLab.com	gitlab.com/owner/repo	Personal Access Token	read_api, read_repository
Self-hosted GitLab	gitlab.example.com/owner/repo	Personal Access Token	read_api, read_repository

License

MIT

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes with tests
4. Run make check to ensure quality
5. Submit a pull request