commit-msg

#!/usr/bin/env bash

#
#  All Contributions by Match Group
#
#  Copyright © 2025 Tinder (Match Group, LLC)
#
#  Licensed under the Match Group Modified 3-Clause BSD License.
#  See https://github.com/Tinder/Commit-Message-Validation-Hook/blob/main/LICENSE for license information.
#

COMMIT_MSG=$(cat "$1" | grep -ve '^#')

LINE_1="$(echo "$COMMIT_MSG" | head -1)"
LINE_2="$(echo "$COMMIT_MSG" | tail -n +2 | head -1)"
LINE_N="$(echo "$COMMIT_MSG" | tail -n +3)"

match()
{
    echo "$1" | grep -e "$2" >/dev/null
}

match "$LINE_1" '\S' || {
    echo >&2 "Aborting commit due to empty commit message."
    exit 1
}

abort()
{
    echo >&2 "Aborting commit due to $1"
    echo >&2 "-"
    echo >&2 "$COMMIT_MSG"
    echo >&2 "-"
    echo >&2 "To temporarily bypass commit message validation, use \`git commit --no-verify\`."
    exit 1
}

match "$LINE_1" '^[[:lower:]]' && \
    abort "first line of commit message starting with a lowercase letter."

match "$LINE_1" '.*\.\s*$' && \
    abort "first line of commit message ending with a period."

match "$LINE_1" '^..\{50\}' && \
    abort "first line of commit message exceeding 50 character limit."

match "$LINE_2" '^$' || \
    abort "second line of commit message not being empty."

match "$LINE_N" '^..\{72\}' && \
    abort "line in body of commit message exceeding 72 character limit."

if command -v spellcheck >/dev/null
then
    MISSPELLED_WORDS=$(echo "$COMMIT_MSG" | spellcheck)
    if [ $? -ne 0 ]
    then
        NEWLINE=$'\n'
        abort "misspelled words:${NEWLINE}${MISSPELLED_WORDS}"
    fi
fi