Use Claude Code to improve your last git commit message

README.md

Git Commit Message Improver

A powerful bash script that uses Claude CLI to automatically improve generic or poorly written git commit messages. It analyses your code changes and suggests more descriptive, conventional commit messages.

Features

• 🤖 AI-Powered: Uses Claude to analyse your changes and generate meaningful commit messages
• 📝 Smart Detection: Automatically identifies generic commit messages like "update", "fix", "changes"
• 🔄 Batch Processing: Can improve all unpushed commits on your current branch
• ⚡ Model Selection: Choose between different Claude models for speed vs quality
• 🎨 Coloured Output: Clear, colourful terminal output for better readability
• ✅ Interactive: Confirms each change before applying
• 🔧 Git Integration: Easy installation as git aliases

Prerequisites

• Git
• Claude CLI installed and authenticated
• Bash shell

Installation

1. Download the script:

   curl -O https://gist.github.com/withakay/9a4b174f8a5a28b8abba3e2ddf23db88#file-git-improve-commit-sh
   chmod +x git-improve-commit.sh

2. Install git aliases (recommended):

   ./git-improve-commit.sh --install

   This creates the following git aliases:

   • git ic - Improve the last commit
   • git ib - Improve all unpushed commits on current branch
   • git improve-commit - Long form of ic
   • git improve-branch - Long form of ib

Usage

Basic Usage

# Improve the last commit (default action)
./git-improve-commit.sh

# Or using git alias after installation
git ic

Improve Multiple Commits

# Improve all unpushed commits on current branch
./git-improve-commit.sh --branch

# Or using git alias
git ib

Model Selection

Use faster models for quicker responses:

# Use Haiku (fastest model)
./git-improve-commit.sh --model claude-3-haiku-20240307

# Or with alias
git ic -m claude-3-haiku-20240307

Set Default Model

# Set a default model in git config
git config --global commit.claude-model claude-3-haiku-20240307

# Now all commands will use Haiku by default
git ic

Available Models

• claude-3-haiku-20240307 - Fastest, good for simple commits
• claude-3-sonnet-20240229 - Balanced speed and quality
• claude-3-opus-20240229 - Highest quality, slower

Configuration

Environment Variables

• DEBUG=1 - Show detailed debug information
• VERBOSE=1 - Show error details
• CLAUDE_MODEL=model-name - Set default model

Example:

DEBUG=1 ./git-improve-commit.sh

Git Config

Store your preferred model permanently:

git config --global commit.claude-model claude-3-haiku-20240307

How It Works

1. Analyses Changes: Extracts the git diff for your commit
2. Detects Generic Messages: Identifies commits with generic messages like "update", "fix", etc.
3. Generates Improvement: Sends the diff and current message to Claude for analysis
4. Suggests Better Message: Claude suggests a conventional commit message
5. Confirms Change: You review and approve the new message
6. Updates Commit: Applies the new message using git commit --amend or interactive rebase

Generic Message Detection

The script automatically detects these patterns as generic:

• Single words: update, fix, changes, updates, fixes, wip, commit, save, done, test, testing, stuff
• Patterns: minor*, small*, quick*, add*

Troubleshooting

Test Claude CLI Connection

./git-improve-commit.sh --test

Debug Mode

DEBUG=1 ./git-improve-commit.sh

Common Issues

1. "claude command not found"

   • Install Claude CLI: Follow instructions at claude-cli repository

2. "No upstream branch found"

   • Set an upstream branch: git push --set-upstream origin branch-name

3. Authentication errors

   • Ensure Claude CLI is properly authenticated
   • Check your API key configuration

Examples

Before and After

Before: add
After: feat: implement user authentication middleware

Before: fix
After: fix: resolve null pointer exception in payment processor

Before: update
After: docs: update API documentation with new endpoints

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License - feel free to use this in your projects!

Acknowledgments

• Powered by Claude from Anthropic
• Inspired by the need for better commit messages in development teams

git-improve-commit.sh

#!/bin/bash
# Git commit message improvement script using Claude CLI
# Can improve the last commit or all unpushed commits on current branch

set -e

# Colour codes for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m' # No Colour

# Default model (empty means use Claude Code's default)
DEFAULT_MODEL=""

# Function to print coloured output
print_colour() {
    local colour=$1
    shift
    echo -e "${colour}$@${NC}"
}

# Function to check if we're in a git repository
check_git_repo() {
    if ! git rev-parse --git-dir > /dev/null 2>&1; then
        print_colour $RED "Error: Not in a git repository"
        exit 1
    fi
}

# Function to check if message is generic
is_generic_message() {
    local msg="$1"
    local msg_lower=$(echo "$msg" | tr '[:upper:]' '[:lower:]' | xargs)

    local generic_patterns=(
        "^update$"
        "^fix$"
        "^changes$"
        "^updates$"
        "^fixes$"
        "^wip$"
        "^commit$"
        "^save$"
        "^done$"
        "^test$"
        "^testing$"
        "^stuff$"
        "^minor.*$"
        "^small.*$"
        "^quick.*$"
        "^add.*$"
    )

    for pattern in "${generic_patterns[@]}"; do
        if [[ "$msg_lower" =~ $pattern ]]; then
            return 0
        fi
    done

    return 1
}

# Function to get improved commit message from Claude
get_improved_message() {
    local original_msg="$1"
    local commit_sha="$2"

    # Get the diff for this commit
    local diff=""
    if [ -z "$commit_sha" ]; then
        # For staged changes
        diff=$(git diff --cached)
    else
        # For existing commit
        diff=$(git show --format="" "$commit_sha")
    fi

    # Check if diff is empty
    if [ -z "$diff" ]; then
        print_colour $YELLOW "Warning: No changes found in commit" >&2
        return 1
    fi

    # Create a temporary file with the context
    local temp_context=$(mktemp)
    cat > "$temp_context" << EOF
The current commit message is: "$original_msg"

Here are the changes:
$diff

Please analyze these changes and provide a better, more descriptive commit message that:
1. Summarizes what was changed
2. Explains why (if apparent from the changes)
3. Follows conventional commit format if possible (feat:, fix:, docs:, etc.)
4. Is concise but informative (ideally under 72 characters for the first line)

Just output the new commit message, nothing else.
EOF

    # Build claude command with optional model
    local claude_cmd="claude -p"
    if [ -n "$CLAUDE_MODEL" ]; then
        claude_cmd="$claude_cmd --model $CLAUDE_MODEL"
    fi

    # Debug mode - show command if DEBUG env var is set
    if [ -n "$DEBUG" ]; then
        print_colour $YELLOW "Debug: Running command: $claude_cmd" >&2
        print_colour $YELLOW "Debug: Context length: $(wc -c < "$temp_context") bytes" >&2
        print_colour $YELLOW "Debug: First 100 chars of diff: ${diff:0:100}..." >&2
    fi

    # Call Claude CLI to improve the message, capture both stdout and stderr
    local error_file=$(mktemp)
    local output_file=$(mktemp)

    # Run the command and capture everything
    # Using proper Claude CLI syntax
    $claude_cmd < "$temp_context" >"$output_file" 2>"$error_file"
    local exit_code=$?

    # Read the output
    local new_msg=$(cat "$output_file")
    local error_msg=$(cat "$error_file")

    # Debug output
    if [ -n "$DEBUG" ]; then
        print_colour $YELLOW "Debug: Exit code: $exit_code" >&2
        print_colour $YELLOW "Debug: Output length: $(echo -n "$new_msg" | wc -c) chars" >&2
        print_colour $YELLOW "Debug: Error output: $error_msg" >&2
        if [ -n "$new_msg" ]; then
            print_colour $YELLOW "Debug: Raw output: '$new_msg'" >&2
        fi
    fi

    # Check for errors
    if [ $exit_code -ne 0 ]; then
        if [ -n "$DEBUG" ] || [ -n "$VERBOSE" ]; then
            print_colour $RED "Error: Claude CLI failed with exit code $exit_code" >&2
            if [ -n "$error_msg" ]; then
                print_colour $RED "Error message: $error_msg" >&2
            fi
        fi

        # Check if claude is installed
        if ! command -v claude &> /dev/null; then
            print_colour $RED "Error: 'claude' command not found. Please install Claude CLI first." >&2
            print_colour $YELLOW "Visit: https://github.com/anthropics/claude-cli" >&2
        fi
    fi

    # Clean up temp files
    rm -f "$temp_context" "$error_file" "$output_file"

    if [ $exit_code -eq 0 ] && [ -n "$new_msg" ]; then
        # Remove any markdown formatting that might be present
        new_msg=$(echo "$new_msg" | sed 's/^```.*//g' | sed 's/```$//g' | xargs)
        echo "$new_msg"
        return 0
    else
        return 1
    fi
}

# Function to confirm action with user
confirm() {
    local prompt="$1"
    local response

    while true; do
        read -p "$prompt (y/n): " response
        case $response in
            [Yy]* ) return 0;;
            [Nn]* ) return 1;;
            * ) echo "Please answer yes (y) or no (n).";;
        esac
    done
}

# Function to improve last commit
improve_last_commit() {
    local commit_sha=$(git rev-parse HEAD)
    local original_msg=$(git log -1 --pretty=%B)

    print_colour $YELLOW "Current commit message: '$original_msg'"

    if [ -n "$CLAUDE_MODEL" ]; then
        print_colour $YELLOW "Using model: $CLAUDE_MODEL"
    fi

    if ! is_generic_message "$original_msg"; then
        print_colour $GREEN "Commit message appears to be descriptive already."
        if ! confirm "Do you want to improve it anyway?"; then
            return 0
        fi
    fi

    print_colour $YELLOW "Using Claude CLI to generate a better commit message..."

    local new_msg=$(get_improved_message "$original_msg" "$commit_sha")

    if [ $? -eq 0 ] && [ -n "$new_msg" ] && [ "$new_msg" != "$original_msg" ]; then
        print_colour $GREEN "Suggested commit message: '$new_msg'"

        if confirm "Apply this commit message?"; then
            git commit --amend -m "$new_msg"
            print_colour $GREEN "✓ Commit message updated successfully!"
        else
            print_colour $YELLOW "Commit message not changed."
        fi
    else
        print_colour $RED "Failed to generate improved message, keeping original"
    fi
}

# Function to improve all unpushed commits on current branch
improve_branch_commits() {
    local upstream=$(git rev-parse --abbrev-ref --symbolic-full-name @{u} 2>/dev/null || echo "")

    if [ -z "$upstream" ]; then
        print_colour $RED "No upstream branch found. Please set an upstream branch first."
        exit 1
    fi

    # Get list of unpushed commits
    local unpushed_commits=$(git rev-list $upstream..HEAD)

    if [ -z "$unpushed_commits" ]; then
        print_colour $YELLOW "No unpushed commits found on current branch."
        return 0
    fi

    local commit_count=$(echo "$unpushed_commits" | wc -l)
    print_colour $YELLOW "Found $commit_count unpushed commit(s) on current branch."

    if [ -n "$CLAUDE_MODEL" ]; then
        print_colour $YELLOW "Using model: $CLAUDE_MODEL"
    fi

    # Process commits from oldest to newest
    local commits_array=()
    while IFS= read -r commit; do
        commits_array+=("$commit")
    done <<< "$(echo "$unpushed_commits" | tac)"

    local improved_count=0

    for commit_sha in "${commits_array[@]}"; do
        local original_msg=$(git log -1 --pretty=%B "$commit_sha")
        print_colour $YELLOW "\nCommit: $commit_sha"
        print_colour $YELLOW "Current message: '$original_msg'"

        local should_improve=false

        if is_generic_message "$original_msg"; then
            print_colour $YELLOW "This appears to be a generic commit message."
            should_improve=true
        else
            if confirm "Do you want to improve this message?"; then
                should_improve=true
            fi
        fi

        if [ "$should_improve" = true ]; then
            print_colour $YELLOW "Generating improved message..."
            local new_msg=$(get_improved_message "$original_msg" "$commit_sha")

            if [ $? -eq 0 ] && [ -n "$new_msg" ] && [ "$new_msg" != "$original_msg" ]; then
                print_colour $GREEN "Suggested message: '$new_msg'"

                if confirm "Apply this commit message?"; then
                    # Use interactive rebase to change the commit message
                    GIT_SEQUENCE_EDITOR="sed -i '1s/pick/reword/'" git rebase -i $commit_sha^
                    GIT_EDITOR="echo '$new_msg' >" git rebase --continue

                    ((improved_count++))
                    print_colour $GREEN "✓ Commit message updated!"
                else
                    print_colour $YELLOW "Skipping this commit."
                fi
            else
                print_colour $RED "Failed to generate improved message for this commit."
            fi
        fi
    done

    print_colour $GREEN "\nSummary: Improved $improved_count out of $commit_count unpushed commits."
}

# Function to install as git alias
install_git_alias() {
    local script_path=$(realpath "$0")

    print_colour $YELLOW "Installing git aliases..."

    # Long form aliases
    git config --global alias.improve-commit "!$script_path"
    git config --global alias.improve-branch "!$script_path --branch"

    # Short form aliases
    git config --global alias.ic "!$script_path"
    git config --global alias.ib "!$script_path --branch"

    print_colour $GREEN "✓ Git aliases installed successfully!"
    print_colour $GREEN "  Long form:"
    print_colour $GREEN "  - Use 'git improve-commit' to improve the last commit"
    print_colour $GREEN "  - Use 'git improve-branch' to improve all unpushed commits on current branch"
    print_colour $GREEN "  Short form:"
    print_colour $GREEN "  - Use 'git ic' to improve the last commit"
    print_colour $GREEN "  - Use 'git ib' to improve all unpushed commits on current branch"
}

# Main script logic
main() {
    # Check for model environment variable or flag
    CLAUDE_MODEL="$DEFAULT_MODEL"

    # Process model flag if present
    while [[ $# -gt 0 ]]; do
        case $1 in
            --model|-m)
                CLAUDE_MODEL="$2"
                shift 2
                ;;
            *)
                break
                ;;
        esac
    done

    check_git_repo

    # Parse command line arguments
    case "${1:-}" in
        --last|-l)
            improve_last_commit
            ;;
        --branch|-b)
            improve_branch_commits
            ;;
        --install)
            install_git_alias
            ;;
        --test)
            # Test claude CLI functionality
            print_colour $YELLOW "Testing Claude CLI installation..."

            if ! command -v claude &> /dev/null; then
                print_colour $RED "✗ claude command not found in PATH"
                exit 1
            fi

            print_colour $GREEN "✓ claude found at: $(which claude)"

            # Try a simple test
            print_colour $YELLOW "Testing claude with a simple prompt..."
            local test_output=$(echo "Say 'Hello' and nothing else" | claude 2>&1)
            local test_exit=$?

            if [ $test_exit -eq 0 ]; then
                print_colour $GREEN "✓ claude is working! Output: $test_output"
            else
                print_colour $RED "✗ claude test failed with exit code: $test_exit"
                print_colour $RED "Error output: $test_output"
                print_colour $YELLOW "\nPossible issues:"
                print_colour $YELLOW "1. Claude CLI may not be authenticated"
                print_colour $YELLOW "2. Network connection issues"
                print_colour $YELLOW "3. Invalid API configuration"
            fi
            ;;
        --help|-h)
            cat << EOF
Git Commit Message Improvement Script

Usage: $0 [OPTIONS]

Options:
    --model, -m MODEL   Use specific Claude model (e.g., claude-3-haiku-20240307)
    --last, -l          Improve the last commit message (default)
    --branch, -b        Improve all unpushed commits on current branch
    --install           Install as git aliases (improve-commit, improve-branch, ic, ib)
                --help, -h          Show this help message

Environment Variables:
    DEBUG=1              Show debug information
    VERBOSE=1            Show error details
    CLAUDE_MODEL=...     Set default model

Model Options:
    You can specify a model in three ways:
    1. Command line: $0 --model claude-3-haiku-20240307
    2. Environment variable: CLAUDE_MODEL=claude-3-haiku-20240307 $0
    3. Git config: git config --global commit.claude-model claude-3-haiku-20240307

    Common fast models:
    - claude-3-haiku-20240307  (fastest, good for simple commits)
    - claude-3-sonnet-20240229 (balanced speed and quality)
    - claude-3-opus-20240229   (highest quality, slower)

Examples:
    $0                                    # Improve last commit with default model
    $0 --model claude-3-haiku-20240307   # Use Haiku (fast) model
    $0 --branch -m claude-3-haiku-20240307 # Improve branch with Haiku
    git ic                                # After installing aliases
    git ib                                # After installing aliases

This script uses Claude CLI to analyze your commits and suggest better,
more descriptive commit messages.
EOF
            ;;
        "")
            # No arguments - default to improving last commit
            improve_last_commit
            ;;
        *)
            print_colour $RED "Error: Invalid option '${1}'. Use --help for usage information."
            exit 1
            ;;
    esac
}

# Check for git config model setting
if [ -z "$CLAUDE_MODEL" ]; then
    GIT_MODEL=$(git config --get commit.claude-model 2>/dev/null || echo "")
    if [ -n "$GIT_MODEL" ]; then
        CLAUDE_MODEL="$GIT_MODEL"
    fi
fi

# Check for environment variable
if [ -n "$CLAUDE_MODEL_ENV" ]; then
    CLAUDE_MODEL="$CLAUDE_MODEL_ENV"
fi

# Run main function
main "$@"