commit-msg

#!/usr/bin/env bash

# This hook ensures we follow Tim Pope's guidelines here:
# https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html

trap cleanup EXIT SIGHUP SIGINT SIGTERM

cleanup() {
    rm clean_msg_file.tmp
}

# Git will pass the commit message to the hook as a file
# MSG_FILE="$1"
# Husky does not pass arguments to hooks, so we
# use this workaround instead.
MSG_FILE='.git/COMMIT_EDITMSG'

# define the expected format of message
SUMMARY_MAX=50
BODY_MAX=72
E_SUMMARY_MSG="❌ Violation: summary length exceeds $SUMMARY_MAX chars"
E_SUMMARY=1 
E_SEPARATOR_MSG="❌ Violation: no blank line separates summary from body"
E_SEPARATOR=2
E_BODY_MSG="❌ Violation: body width exceeds $BODY_MAX chars"
E_BODY=3 
E_ONLY_COMMENTS_MSG="❌ Error: message contains only comments"
E_ONLY_COMMENTS=4

RETVAL=0

grep -v '^#' "$MSG_FILE" > clean_msg_file.tmp
if ! grep -v -q '^[[:space:]]*$' clean_msg_file.tmp; then
     # nothing for our hook to check
     echo "$E_ONLY_COMMENTS_MSG"
     exit $E_ONLY_COMMENTS
fi

summary_length=`head -1 clean_msg_file.tmp | wc -m`  # always use 'm' option with wc to count characters not bytes
if [ $summary_length -gt $SUMMARY_MAX ]; then
    echo "$E_SUMMARY_MSG"
    RETVAL=$E_SUMMARY
fi

num_lines=`wc -l < clean_msg_file.tmp`

if [ "$num_lines" -gt 1 ]; then
    if ! head -2 clean_msg_file.tmp | tail -1 | grep -q '^[[:space:]]*$'; then
        echo "$E_SEPARATOR_MSG"
        RETVAL=$E_SEPARATOR
    fi
fi

if [ "$num_lines" -gt 2 ]; then
    while read line; do
        num_chars=`echo $line | wc -m`
        if [ $num_chars -gt $BODY_MAX ]; then
            echo "$E_BODY_MSG"
            RETVAL=$E_BODY
            break
        fi
    done < <(tail -n +3 clean_msg_file.tmp)
fi

exit $RETVAL