¬ just serendipity 🍀 (not just serendipity)

Problem statement: auto-generate a commit message for git from the command-line. The solution should be vendor agnostic.

Given a git-foo.sh in $PATH, it can be invoked as git foo, as if it were a built-in git command.

This is helpful to enable seamless integration with git. I chose to call the subcommand aicommit. I suppose commit-ai would also be sensible.

The goal is to create git-aicommit.sh in ~/.bin (which is in my $PATH via my .dotfiles)

This initial draft worked well:

#!/bin/bash
#
# git-aicommit - Create a commit with an AI-generated title based on staged changes

set -e

# Check if we're inside a git repository
if [ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" != "true" ]; then
  echo "Error: Not in a git repository"
  exit 1
fi

# Check if there are staged changes
if git diff --cached --quiet; then
  echo "Error: No staged changes to commit"
  exit 1
fi

# Select AI agent (default: claude)
agent="${GIT_AI_AGENT:-claude}"
case "$agent" in
  # keep-sorted start
  amp|ampcode)
    ai_prompt() { amp -x "$1"; }
    ;;
  claude)
    ai_prompt() { claude -p "$1"; }
    ;;
  # keep-sorted end
  *)
    echo "Error: Unknown AI agent: $agent"
    exit 1
    ;;
esac

prompt="Look at the staged git changes and create a summarizing git commit title. Only respond with the title and no affirmation."

# Generate commit message and commit
echo "Generating commit message with $agent..."
git commit -m "$(ai_prompt "$prompt")" "$@"

echo "AI commit created successfully"

Refer to this source for an up-to-date version as it evolves.

Let’s break it down:

• Previously: we employ an oneshot command to call an LLM agent, so that there’s no need to do it interactively. Initially I added only Claude Code and Amp because they are the agents I use the most; perhaps this list will be expanded later on but it is not intended to be exhaustive¹.
• The command is intended to run in O(seconds). If it takes too long, then it should be simplified (via a better prompt).
• By default it uses Claude. To use another agent, call it like:

GIT_AI_AGENT="amp" git aicommit

This preference could be trivially made persistent on a per-repo basis by using direnv. For example, use Claude at work and Amp in personal git repositories².

Later on I split the command into two: git aicommit and git aicommit-quick. “Quick” populates the commit message title only (think git commit -m "foo"), whereas the non-quick version populates the body as well, accounting for GitHub PR templates when they exist. Time will tell whether I need this distinction.