#!/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)

case "$lcp" in
	[^.]*/*) prepend_msg "$(echo "$lcp" | cut -d/ -f1-2): ";;
esac

exit 0