get commit message in git hook

Question

I would like to check commit message before git commit. I use pre-commit hook to do that, but couldn\'t find the way to get commit message in .git/pre-commit script. How cou

Answer 1

You can do the following in a pre-receive hook (for server side) using Python, and that will display the revision information.

import sys
import subprocess
old, new, branch = sys.stdin.read().split()
proc = subprocess.Popen(["git", "rev-list", "--oneline","--first-parent" , "%s..%s" %(old, new)], stdout=subprocess.PIPE)
commitMessage=str(proc.stdout.readlines()[0])  

Answer 2

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

Answer 3

The hook name should be:

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

Answer 4

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}