Add git-change-commit

#!/bin/bash

OPTS_SPEC="\

git change-commit [-h] [--start|--continue|--reset|--abort] [REVISION] [[--] PATH [PATH]]

change-commit does an interactive rebase keeping the current changes in the

working directory, allowing edits to be made to commits using changes made

in the working directory.

If more than one revision is given, only the first will be used.

This comes with the standard warning:

  DO NOT CHANGE COMMITS THAT HAVE BEEN (OR COULD HAVE BEEN) PUSHED OR FETCHED

  TO OTHER REPOSITORIES OUTSIDE OF YOUR CONTROL.

  (Unless you really, *really* know what you are doing.)

--

h,help  show this message and exit

start  begin the rebase, this is the default action and is optional. Requires: REVISION

reset  reset the working directory to the state it was in before starting. Optional: REVISION, PATH...

continue  continue to the next commit marked for editing

abort  quit the changes and return to the originally checked out commit/head

"

parse() { eval "$(git rev-parse --parseopt -- "$@" <<< "$OPTS_SPEC" || echo return $?)"; }

die() {

	EXIT_STATUS=${EXIT_STATUE-$?}

	[ "x$1" = x--usage ] && parse --help

	echo "$*"

	exit $EXIT_STATUS

} >&2

error() { printf "WARNING: %s\n" "$*"; } >&2

REPO_DIR=`git rev-parse --git-dir` || die

STASH_FILE=$REPO_DIR/change-commit/stash

STASH_FILE_BACKUP=${STASH_FILE}_pref

is_active() { [ -d $REPO_DIR/rebase-merge ]; }

is_ours() { [ -e $STASH_FILE ]; }

confirm()

{

	local prompt=$1 ans

	while true; do

		read -p "$prompt (y|N) " ans

		case $ans in

			y*|Y*) return 0 ;;

			n*|N*|'') return 1 ;;

			*) prompt="Sorry, what did you mean?" ;;

		esac

	done

}

action_start()

{

	local stash=$(git stash create) || die

	[ -n "$REVISION" ] || die "need a revision to edit"

	git reset --hard

	git rebase -i $REVISION~ 2>/dev/null

	mkdir -p $(dirname $STASH_FILE)

	if ! echo "$stash" > $STASH_FILE; then

		error "could not write stash ID to $STASH_FILE, aborting"

		git rebase --abort

	fi

	cp $STASH_FILE $STASH_FILE_BACKUP

	[ -n "$stash" ] && git stash apply $stash

}

action_continue()

{

	local stash=$(git stash create) || die

	echo "$stash" >> $STASH_FILE || die

	git reset --hard

	git rebase --continue || die

	[ -n "$stash" ] && git stash apply $stash

	is_active || rm $STASH_FILE

}

action_reset()

{

	local stash=$(head -n1 $STASH_FILE_BACKUP) || die

	if [ ${#PATHS[*]} -gt 0 ]; then

		git checkout ${REVISION:-$stash} -- "${PATHS[@]}"

	elif [ -n "$REVISION" ]; then

		error "This will reset the working directory to match $REVISION, are" \

		      "you sure this is what you intended?"

		error "You will still be able to get the original working directory" \

		      "by running --reset without any further arguments."

		confirm "Reset to ${REVISION::10}?" || return 0

		local saved_head=$(git symbolic-ref -q HEAD || cat $REPO_DIR/HEAD)

		git reset --hard HEAD

		git checkout $REVISION

		git reset $saved_head

	else

		git reset --hard

		[ -n "$stash" ] && git stash apply $stash

	fi

}

action_abort()

{

	local stash=$(head -n1 $STASH_FILE)

	git rebase --abort

	[ -n "$stash" ] && git stash apply $stash

	rm $STASH_FILE

}

# normalise cmdline arguments

parse "$@" || exit $?

ACTION=action_start

while [ $# -gt 0 ]; do

	case $1 in

		--continue)

			is_active && is_ours || \

				die "--continue given, but no active changes being made"

			ACTION=action_continue

			;;

		--reset)

			is_ours || \

				die "--reset given, but no stashed changes available"

			ACTION=action_reset

			;;

		--abort)

			is_ours || \

				die "--abort given, but no active changes being made"

			ACTION=action_abort

			;;

		--start)

			is_active && die "already doing a rebase or change"

			ACTION=action_start

			;;

		*)

			REVISION=$(git rev-parse --revs-only "$@" | head -n1)

			PATHS=( $(git rev-parse --sq --no-revs --no-flags "$@") )

			break

			;;

	esac

	shift

done

$ACTION

exit $?