#!/bin/sh
#
# This hook adds prefix "<repo>/<pkgname>: " to the commit message when
# committing changes of a single package.
#
MSG_FILE="$1"
SOURCE="$2"

longest_common_prefix() {
	awk -F/ '
		(NR == 1) { split($0, prefix); prefix_len = NF }
		(NR > 1) {
			for (i = 1; i <= prefix_len; i++) {
				if (prefix[i] != $i) {
					prefix_len = i - 1; break
				}
			}
		}
		(prefix_len == 0) { exit }
		END {
			res = prefix[1]
			for (i = 2; i <= prefix_len; i++) {
				res = res FS prefix[i]
			}
			print(res)
		}'
}

prepend_msg() {
	local prefix="$1"

	printf '%s\n%s\n' "$prefix" "$(cat "$MSG_FILE")" > "$MSG_FILE"
}


# Do nothing if message has been given using -m, template, merge etc.
[ -z "$SOURCE" ] || exit 0

lcp=$(git diff-index --name-only --cached HEAD | longest_common_prefix)
prefix=""

case "$lcp" in
	extra-repos/systemd/systemd/*)
		prefix="systemd"
		;;
	extra-repos/systemd/*)
		prefix="systemd/$(echo "$lcp" | cut -d/ -f3)"
		;;
	device/*/*)
		prefix="$(echo "$lcp" | cut -d/ -f3)"
		;;
	docs/*.adoc)
		prefix="docs/$(basename $lcp .adoc)"
		;;
	docs/*)
		prefix="docs"
		;;
	device/*)
		# Multiple packages touched for same device category. More
		# logic could be added to detect if they all belong to same
		# device.
		;;
	[^.]*/*)
		prefix="$(echo "$lcp" | cut -d/ -f1-2)"
		;;
esac

if [ -n "$prefix" ]; then
	prepend_msg "$prefix: "
fi

exit 0