#!/usr/bin/env bash
#
# Undo a commit or a series of commits.
# Copyright (c) Matt Porter, 2005
# Copyright (c) Petr Baudis, 2005
#
# Takes a commit ID which is the earliest commit to be removed from
# the repository. If no parameter is passed, it uncommits the latest
# commit ('HEAD'). Read the CAVEATS section before using it for the
# first time.
#
# This command is a close relative of `cg-switch -f` (which does
# essentially the same thing, but is slightly more powerful at the
# expense of a more elaborate usage). Do not confuse either with the
# operation performed by `cg-seek`, which is meant only for temporary
# excursions to the project history.
#
# OPTIONS
# -------
# -t:: Restore the working copy of the previous commit
#	This optional parameter makes `cg-admin-uncommit` to roll back
#	the tree as well to the previous commit. Without this option
#	(by default) 'Cogito' keeps the tree in its current state,
#	therefore generating tree with local changes against the target
#	commit, consisting of the changes in the rolled back commits.
#
# CAVEATS
# -------
# This command can be dangerous! It is safe to do as long as you do not
# push the commit out in the meantime, but you should 'NEVER' uncommit an
# already pushed out commit. Things will break for the fetchers since you
# just broke the fast-forward merging mechanism (the new commit is not
# descendant of the previous one), and the push command will refuse to
# push again after you uncommitted a pushed out commit, too. At the moment
# you pushed the commit out it's etched to the history, live with that.

USAGE="cg-admin-uncommit [-t] [COMMIT_ID]"
_git_requires_root=1

. "${COGITO_LIB}"cg-Xlib || exit 1

[ -s "$_git/blocked" ] && die "uncommitting blocked: $("cat $_git/blocked")"

rollback_tree=
while optparse; do
	if optparse -t; then
		rollback_tree=1
	else
		optfail
	fi
done


base="$(cg-object-id -c)" || exit 1

commit="$(cg-object-id -c "${ARGS[0]}")" || exit 1
[ "$(git-rev-list $commit ^$base)" ] && \
	die "$commit: not an ancestor of HEAD"

parent="$(cg-object-id -p "$commit")" || exit 1
[ "$parent" ] || die "cannot rewind behind the initial commit"
[ "$(echo "$parent" | wc -l)" -gt 1 ] &&
	die "cannot rewind merges; please 'cg-switch -f -r parentid $_git_head' instead"


echo "Rewinding $base (HEAD) -> $parent" >&2

tree_timewarp "backwards" "$rollback_tree" "$base" "$parent"
exit 0