#!/usr/bin/env bash
#
# git-rename-branches - rename multiple branches that start with a given name
#
#    Copyright (C) 2012 Rodrigo Silva (MestreLion) <linux@rodrigosilva.com>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program. If not, see <http://www.gnu.org/licenses/gpl.html>

usage() {
cat <<- USAGE
	Usage: $self [options] BRANCH_PREFIX  NEW_PREFIX
USAGE
if [[ "$1" ]] ; then
	cat <<- USAGE
		Try '$self --help' for more information.
	USAGE
	exit 1
fi
cat <<-USAGE

	Batch renames branches with a matching prefix to another prefix

	Options:
	-h|--help     - show this page.
	-v|--verbose  - print more details about what is being done.
	-n|--dry-run  - do not actually renames the branches.

	BRANCH_PREFIX - a prefix that matches the start of branch names
	NEW_PREFIX    - the new prefix for the branch names

	Examples:
	$ git-rename-branches bug bugfix
	bug/128  -> bugfix/128
	bug_test -> bugfix_test

	$ git-rename-branches ma backup/ma
	master -> backup/master
	main   -> backup/main

	Copyright (C) 2012 Rodrigo Silva (MestreLion) <linux@rodrigosilva.com>
	License: GPLv3 or later. See <http://www.gnu.org/licenses/gpl.html>
USAGE
exit 0
}
invalid() { echo "$self: invalid option $1" ; usage 1 ; }
missing() { echo "$self: missing ${1:+$1 }operand" ; usage 1 ; }

self="${0##*/}"
verbose=0
dry_run=0

# Loop options
while (( $# )); do
	case "$1" in
	-h|--help     ) usage                ;;
	-v|--verbose  ) verbose=1            ;;
	-n|--dry-run  ) dry_run=1            ;;
	--            ) shift        ; break ;;
	-*            ) invalid "$1" ; break ;;
	*             )                break ;;
	esac
	shift
done

[[ "$1" && "$2" ]] || missing 'a PREFIX'

while read -r branch; do
	if ((dry_run)) ; then
		((verbose)) && echo "$branch -> ${2}${branch#$1}"
	else
		git branch -m "$branch" "${2}${branch#$1}" &&
			((verbose)) && echo "$branch -> ${2}${branch#$1}"
	fi
done < <(git branch | awk -v branches="${1/\\/\\\\}" '$NF ~ "^" branches {print $NF}')
