get commit message in git hook

In the pre-commit hook, the commit message usually hasn't been created yet 1. You probably want to use one of the prepare-commit-msg or commit-msg hooks instead. There's a nice section in Pro Git on the order in which these hooks are run, and what you typically might do with them.

1. The exception is that the committer might have supplied a commit message with -m, but the message still isn't accessible to the pre-commit hook, whereas it is to prepare-commit-msg or commit-msg


The hook name should be:

commit-msg , otherwise it won't get invoked:


I have created a commit-msg script in Bash having the commit syntax <CURRENT_BRANCH_NAME>-<4_DIGIT_TICKETID>-<COMMIT_DECRIPTION>. This syntax can be used for Azure DevOps ticket ID-based commits by the developer.

#!/bin/sh

# The below input_file is file ".git/COMMIT_EDITMSG" where commits are stored
INPUT_FILE=$1

# It will copy the commit string from ".git/COMMIT_EDITMSG"
START_LINE=`head -n1 $INPUT_FILE`

# Initial index value
sum=0

# Add commit in an array variable separated by -
IFS='- ' read -r -a array_value <<< "$START_LINE"

# Count array index
for i in ${!array_value[@]}
do
    sum=`expr $sum + $i`
done

# Verify commit
if [ ${sum} == 3 ]; then

BRANCH_NAME=`git branch | awk '/\*/ { print $2; }'`
TICKET_DIGIT=`awk -F '[0-9]' '{print NF-1}' <<< "${array_value[1]}"`

   if [ ${array_value[0]} != ${BRANCH_NAME} ];  then
        echo "please enter current branch name"
        exit 1
   fi

   if [ "${TICKET_DIGIT}" != "4" ];  then
        echo "INVALID TICKET ID"
        exit 1
   else
      echo "verify ticket ID ${array_value[1]}"
   fi

else
   echo "pattern must be <CURRENT_BRANCH_NAME>-<4_DIGIT_TICKETID>-<COMMIT_DECRIPTION> without space and don't use - in commit_description"
   exit 1
fi

I implemented this in the commit-msg hook. See the documentation.

commit-msg

This hook is invoked by git commit, and can be bypassed with the --no-verify option.
It takes a single parameter, the name of the file that holds the proposed commit log message.
Exiting with a non-zero status causes the git commit to abort.

Under my_git_project/.git/hooks, I added the file commit-msg (has to be this name). I added the following Bash contents inside this file which did the validation.

#!/usr/bin/env bash
INPUT_FILE=$1
START_LINE=`head -n1 $INPUT_FILE`
PATTERN="^(MYPROJ)-[[:digit:]]+: "
if ! [[ "$START_LINE" =~ $PATTERN ]]; then
  echo "Bad commit message, see example: MYPROJ-123: commit message"
  exit 1
fi

Tags:

Hook

Git