#!/bin/sh
#
# Copyright (c) 2005 Linus Torvalds
# Copyright (c) 2005 Junio C Hamano
#

case "$0" in
*-revert* )
	test -t 0 && edit=-e
	me=revert
	USAGE='[--edit | --no-edit] [-n] <commit-ish>' ;;
*-cherry-pick* )
	edit=
	me=cherry-pick
	USAGE='[--edit] [-n] [-r] <commit-ish>'  ;;
* )
	die "What are you talking about?" ;;
esac
. git-sh-setup

no_commit= replay=
while case "$#" in 0) break ;; esac
do
	case "$1" in
	-n|--n|--no|--no-|--no-c|--no-co|--no-com|--no-comm|\
	    --no-commi|--no-commit)
		no_commit=t
		;;
	-e|--e|--ed|--edi|--edit)
		edit=-e
		;;
	--n|--no|--no-|--no-e|--no-ed|--no-edi|--no-edit)
		edit=
		;;
	-r|--r|--re|--rep|--repl|--repla|--replay)
		replay=t
		;;
	-*)
		usage
		;;
	*)
		break
		;;
	esac
	shift
done

test "$me,$replay" = "revert,t" && usage

case "$no_commit" in
t)
	# We do not intend to commit immediately.  We just want to
	# merge the differences in.
	head=$(git-write-tree) ||
		die "Your index file is unmerged."
	;;
*)
	head=$(git-rev-parse --verify HEAD) ||
		die "You do not have a valid HEAD"
	files=$(git-diff-index --cached --name-only $head) || exit
	if [ "$files" ]; then
		die "Dirty index: cannot $me (dirty: $files)"
	fi
	;;
esac

rev=$(git-rev-parse --verify "$@") &&
commit=$(git-rev-parse --verify "$rev^0") ||
	die "Not a single commit $@"
prev=$(git-rev-parse --verify "$commit^1" 2>/dev/null) ||
	die "Cannot run $me a root commit"
git-rev-parse --verify "$commit^2" >/dev/null 2>&1 &&
	die "Cannot run $me a multi-parent commit."

# "commit" is an existing commit.  We would want to apply
# the difference it introduces since its first parent "prev"
# on top of the current HEAD if we are cherry-pick.  Or the
# reverse of it if we are revert.

case "$me" in
revert)
	git-rev-list --pretty=oneline --max-count=1 $commit |
	sed -e '
		s/^[^ ]* /Revert "/
		s/$/"/'
	echo
	echo "This reverts $commit commit."
	test "$rev" = "$commit" ||
	echo "(original 'git revert' arguments: $@)"
	base=$commit next=$prev
	;;

cherry-pick)
	pick_author_script='
	/^author /{
		s/'\''/'\''\\'\'\''/g
		h
		s/^author \([^<]*\) <[^>]*> .*$/\1/
		s/'\''/'\''\'\'\''/g
		s/.*/GIT_AUTHOR_NAME='\''&'\''/p

		g
		s/^author [^<]* <\([^>]*\)> .*$/\1/
		s/'\''/'\''\'\'\''/g
		s/.*/GIT_AUTHOR_EMAIL='\''&'\''/p

		g
		s/^author [^<]* <[^>]*> \(.*\)$/\1/
		s/'\''/'\''\'\'\''/g
		s/.*/GIT_AUTHOR_DATE='\''&'\''/p

		q
	}'
	set_author_env=`git-cat-file commit "$commit" |
	LANG=C LC_ALL=C sed -ne "$pick_author_script"`
	eval "$set_author_env"
	export GIT_AUTHOR_NAME
	export GIT_AUTHOR_EMAIL
	export GIT_AUTHOR_DATE

	git-cat-file commit $commit | sed -e '1,/^$/d'
	case "$replay" in
	'')
		echo "(cherry picked from $commit commit)"
		test "$rev" = "$commit" ||
		echo "(original 'git cherry-pick' arguments: $@)"
		;;
	esac
	base=$prev next=$commit
	;;

esac >.msg

# This three way merge is an interesting one.  We are at
# $head, and would want to apply the change between $commit
# and $prev on top of us (when reverting), or the change between
# $prev and $commit on top of us (when cherry-picking or replaying).

echo >&2 "First trying simple merge strategy to $me."
git-read-tree -m -u $base $head $next &&
result=$(git-write-tree 2>/dev/null) || {
    echo >&2 "Simple $me fails; trying Automatic $me."
    git-merge-index -o git-merge-one-file -a || {
	    echo >&2 "Automatic $me failed.  After fixing it up,"
	    echo >&2 "you can use \"git commit -F .msg\""
	    case "$me" in
	    cherry-pick)
		echo >&2 "You may choose to use the following when making"
		echo >&2 "the commit:"
		echo >&2 "$set_author_env"
	    esac
	    exit 1
    }
    result=$(git-write-tree) || exit
}
echo >&2 "Finished one $me."

# If we are cherry-pick, and if the merge did not result in
# hand-editing, we will hit this commit and inherit the original
# author date and name.
# If we are revert, or if our cherry-pick results in a hand merge,
# we had better say that the current user is responsible for that.

case "$no_commit" in
'')
	git-commit -n -F .msg $edit
	rm -f .msg
	;;
esac
