llm powered git commit message

prepare_commit_msg

#!~/.local/share/uv/tools/llm/bin/python

"""
Git hook script for automatically generating commit messages using llm.

Installation:
1. Install `llm` if not already installed:
   uv tool install llm

2. Install and configure a model (e.g., gemini):

   llm install llm-gemini
   llm keys set gemini
   <paste>
   llm models default gemini-2.0-flash

3. Save this script as `.git/hooks/prepare-commit-msg` inside your repository.

4. Make it executable:
   chmod +x .git/hooks/prepare-commit-msg

Now, whenever you commit, the hook will automatically generate a commit message based on staged changes.
"""

import subprocess
import sys
from pathlib import Path

import llm


def get_staged_diff():
    """Obtain the staged diff."""
    result = subprocess.run(["git", "diff", "--staged"], capture_output=True, text=True)
    return result.stdout


def generate_commit_message(diff):
    """Use llm to generate a commit message based on the diff."""
    model_name = llm.get_default_model()  # Get the configured model name
    model = llm.get_model(model_name)  # Retrieve the actual model instance
    prompt = f"Generate a concise commit message for the following diff:\n{diff}"
    response = model.prompt(prompt)  # Get the response directly
    return response.text().strip()  # Use .text() to extract the generated message


def main():
    if len(sys.argv) < 2:
        print("Usage: prepare-commit-msg <commit-msg-file> [commit-source] [SHA1]")
        sys.exit(1)

    commit_msg_path = Path(sys.argv[1])
    diff = get_staged_diff()
    if not diff.strip():
        print("No staged changes detected.")
        sys.exit(1)

    commit_message = generate_commit_message(diff)
    print("\nSuggested commit message:\n")
    print(commit_message)

    # Overwrite the commit message file only if it's a new commit (not amend, merge, or rebase)
    if len(sys.argv) == 2:  # Only modify if it's an interactive commit
        commit_msg_path.write_text(commit_message, encoding="utf-8")


if __name__ == "__main__":
    main()