prepare-commit-msg

#!/bin/bash
#
# This hook adds guidance about the commit message format
# on top of the default commit message.
#
# Called by "git commit" with the name of the file that has the commit message,
# followed by the description of the commit message's source.
#
# To enable this hook, set the hooksPath in git:
# git config core.hooksPath .dev/githooks

COMMIT_MSG_FILE=$1
COMMIT_SOURCE=$2
SHA1=$3

scopes_file=".dev/scopes.txt"
test -r $scopes_file &&
  scopes="$(cat "$scopes_file" | sed '/^\(#.*\|\)$/d' | sed ':a;N;s/\n/, /g;ta')"

beginswith() { case $2 in "$1"*) true;; *) false;; esac; }

# https://mincong.io/2019/07/23/prepare-commit-message-using-git-hook
# Only add custom message when there is no commit source ($COMMIT_SOURCE is empty).
# Otherwise, keep the default message proposed by Git.
# Possible commit sources: message, template, merge, squash or commit.
# See https://git-scm.com/docs/githooks
original=$(cat "$COMMIT_MSG_FILE")
if test -z "$COMMIT_SOURCE"
then
  # Find common path prefix of changed files
  path=$(while read file
    do test -z "$count" && common="$file" && count=$(expr length "$file") ||
      while expr substr "$file" $count 1 != substr "$common" $count 1 >/dev/null; do let count--; done
    done <<<"$(git -P diff --cached --name-only -r)" &&
      expr substr "$common" 1 "$count")
  {
    # Infer type & scope from changed files
    expr "$path" : ".dev" >/dev/null &&
      printf "feat(dev): "
    # Example for gradle projects
    expr "$path" : "gradle" \| "$path" : "build" >/dev/null &&
      printf "chore(gradle): "

    printf "\n\n# Please enter the message in the format\n"
    echo "# <type>(<scope>): <description>"
    echo "# Possible types: fix, feat, docs, style, refactor, test, chore"
    test -n "$scopes" && echo "# Allowed scopes: $scopes"
    echo "# For details see https://kull.jfischer.org"
    echo "$original"
  } > "$COMMIT_MSG_FILE"
fi