prepare-commit-msg-hook

#!/bin/bash

# Get the name of the file containing the commit message
COMMIT_MSG_FILE="$1"

# Read the commit message content only once
COMMIT_MESSAGE_CONTENT=$(cat "$COMMIT_MSG_FILE")

# Check if the commit message is empty (initial commit case) and skip the hook
if [ -z "$COMMIT_MESSAGE_CONTENT" ]; then
    exit 0
fi

# Check if we are in a rebase operation, if so skip processing and exit
if git rev-parse --verify HEAD &>/dev/null; then
    REBASE_HEAD=$(git rev-parse --git-dir)/rebase-apply/head
    if [ -f "$REBASE_HEAD" ]; then
        # echo "Rebase in progress, skipping commit message generation."
        exit 0
    fi

    REBASE_MERGE=$(git rev-parse --git-dir)/rebase-merge/head
    if [ -f "$REBASE_MERGE" ]; then
        # echo "Rebase in progress, skipping commit message generation."
        exit 0
    fi
fi

# Check if there is a non-comment line in the commit message, if so, don't overwrite.
# Simplified grep to check for non-comment, non-empty lines
if sed '/^# ------------------------ >8 ------------------------$/,$d' <<<"$COMMIT_MESSAGE_CONTENT" |\
     grep -vE '^\s*(#|$)' |\
     grep . > /dev/null ; then
  # echo "Existing commit message found, skipping message update."
  exit 0
fi

# Craft the prompt for llm
PROMPT="You are a commit message generator.
Please create a concise and well-formatted commit message, following conventional commits format (e.g., feat: Added a new feature, fix: Resolved a bug, etc.).
The message should be no longer than 50 characters for the first line.
Follow up lines should be wrapped at 72 characters and provide commentary to help reviewer/reader better understand the change.
Here's the existing verbose commit message:

Verbose commit message:
\`\`\`
$COMMIT_MESSAGE_CONTENT
\`\`\`

Commit message:"

# Use llm to generate the commit message.
GENERATED_MESSAGE=$(llm -m gemini-2.0-flash-exp "$PROMPT")

# Check if the generated message is empty or no generation happens and skip replacing
if [ -z "$GENERATED_MESSAGE" ]; then
  echo "No commit message generated from llm, skipping message update"
  echo "$COMMIT_MESSAGE_CONTENT" >> "$COMMIT_MSG_FILE"
  exit 0
fi

# Replace the content of the commit message file with the new message
echo "$GENERATED_MESSAGE" > "$COMMIT_MSG_FILE"
echo "$COMMIT_MESSAGE_CONTENT" >> "$COMMIT_MSG_FILE"

exit 0