#!/bin/bash
#
# Copyright Bart Trojanowski <bart@jukie.net>
# 
# git-wip is a script that will manage Work In Progress (or WIP) branches.
# WIP branches are mostly throw away but identify points of development
# between commits.  The intent is to tie this script into your editor so
# that each time you save your file, the git-wip script captures that
# state in git.  git-wip also helps you return back to a previous state of
# development.
#
# See also http://github.com/bartman/git-wip
#
# The code is licensed as GPL v2 or, at your option, any later version.
# Please see http://www.gnu.org/licenses/gpl-2.0.txt
#

USAGE='[ save <message> [ --editor | --untracked | --no-gpg-sign ] | delete ] [ [--] <file>... ]'
LONG_USAGE="Manage Work In Progress branches

Commands:
        git wip                   - create a new WIP commit
        git wip save <message>    - create a new WIP commit with custom message

Options for save:
        -e --editor               - be less verbose, assume called from an editor
        -u --untracked            - capture also untracked files
        -i --ignored              - capture also ignored files
        --no-gpg-sign             - do not sign commit; that is, countermand
                                    'commit.gpgSign = true'
"

. "$(git --exec-path)/git-sh-setup"

require_work_tree

TMP=$(mktemp -d -t .git-wip)

cleanup () {
	rm -f "$TMP-*"
}

trap cleanup 0

WIP_INDEX="$TMP-INDEX"

WIP_PREFIX=refs/wip/
WIP_COMMAND=
WIP_MESSAGE=WIP
EDITOR_MODE=false

dbg() {
	if test -n "$WIP_DEBUG"
	then
		printf '# %s\n' "$*"
	fi
}

# some errors are not worth reporting in --editor mode
report_soft_error () {
	$EDITOR_MODE && exit 0
	die "$@"
}

get_work_branch () {
	ref=$(git symbolic-ref -q HEAD) \
	|| report_soft_error "git-wip requires a branch"


	branch=${ref#refs/heads/}
	if [ $branch = $ref ] ; then
		die "git-wip requires a local branch"
	fi

	echo $branch
}

check_files () {
	local -a files="$@"

	for f in "${files[@]}"
	do
		[ -f "$f" -o -d "$f" ] || die "$f: No such file or directory."
	done
}

build_new_tree () {
	local untracked=$1 ; shift
	local ignored=$1 ; shift
	local files="$@"

	(
	set -e
	rm -f "$WIP_INDEX"
	cp -p "$GIT_DIR/index" "$WIP_INDEX"
	export GIT_INDEX_FILE="$WIP_INDEX"
	git read-tree $wip_parent
	if [ -n "$files" ]
	then
		git add -f "${files[@]}"
	else
		git add --update .
	fi
	[ -n "$untracked" ] && git add .
	[ -n "$ignored" ] && git add -f -A .
	git write-tree
	rm -f "$WIP_INDEX"
	)
}

do_save () {
	local msg="$1" ; shift
	local add_untracked=
	local add_ignored=
	local no_sign=

	while test $# != 0
	do
		case "$1" in
		-e|--editor)
			EDITOR_MODE=true
			;;
		-u|--untracked)
			add_untracked=t
			;;
		-i|--ignored)
			add_ignored=t
			;;
		--no-gpg-sign)
			no_sign=--no-gpg-sign
			;;
		--)
			shift
			break
			;;
		*)
			[ -f "$1" ] && break
			die "Unknown option '$1'."
			;;
		esac
		shift
	done
	local files="$@"
	local "add_untracked=$add_untracked"
	local "add_ignored=$add_ignored"

	if test ${#files} -gt 0
	then
		check_files "${files[@]}"
	fi

	dbg "msg=$msg"
	dbg "files=$files"

	local work_branch=$(get_work_branch)
	local wip_branch="$WIP_PREFIX$work_branch"

	dbg "work_branch=$work_branch"
	dbg "wip_branch=$wip_branch"

	# enable reflog
	local wip_branch_file="$GIT_DIR/logs/$wip_branch"
	dbg "wip_branch_file=$wip_branch_file"
	mkdir -p "$(dirname "$wip_branch_file")"
	: >>"$wip_branch_file"

	if ! work_last=$(git rev-parse --verify $work_branch)
	then
		report_soft_error "'$work_branch' branch has no commits."
	fi

	dbg "work_last=$work_last"

	if wip_last=$(git rev-parse --quiet --verify $wip_branch)
	then
		local base=$(git merge-base $wip_last $work_last) \
		|| die "'work_branch' and '$wip_branch' are unrelated."

		if [ $base = $work_last ] ; then
			wip_parent=$wip_last
		else
			wip_parent=$work_last
		fi
	else
		wip_parent=$work_last
	fi

	dbg "wip_parent=$wip_parent"

	new_tree=$( build_new_tree "$add_untracked" "$add_ignored" "${files[@]}" ) \
	|| die "Cannot save the current worktree state."

	dbg "new_tree=$new_tree"

	if git diff-tree --exit-code --quiet $new_tree $wip_parent ; then
		report_soft_error "no changes"
	fi

	dbg "... has changes"

	new_wip=$(printf '%s\n' "$msg" | git commit-tree $no_sign $new_tree -p $wip_parent 2>/dev/null) \
	|| die "Cannot record working tree state"

	dbg "new_wip=$new_wip"

	msg1=$(printf '%s\n' "$msg" | sed -e 1q)
	git update-ref -m "git-wip: $msg1" $wip_branch $new_wip $wip_last

	dbg "SUCCESS"
}

if test $# -eq 0
then
	dbg "no arguments"

	do_save "WIP"
	exit $?
fi

dbg "args: $@"

case "$1" in
save)
	WIP_COMMAND=$1
	shift
	if [ -n "$1" ]
	then
		WIP_MESSAGE="$1"
		shift
	fi
	;;
--*)
	;;
*)
	[ -f "$1" ] || die "Unknown command '$1'."
	;;
esac

case $WIP_COMMAND in
save)
	do_save "$WIP_MESSAGE" $@
	;;
*)
	usage
	exit 1
	;;
esac

# vim: set noet sw=8