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

USAGE='[--onto <newbase>] <upstream> [<branch>]'
LONG_USAGE='git-rebase applies to <upstream> (or optionally to <newbase>) commits
from <branch> that do not appear in <upstream>. When <branch> is not
specified it defaults to the current branch (HEAD).

When git-rebase is complete, <branch> will be updated to point to the
newly created line of commit objects, so the previous line will not be
accessible unless there are other references to it already.

Assuming the following history:

          A---B---C topic
         /
    D---E---F---G master

The result of the following command:

    git-rebase --onto master~1 master topic

  would be:

              A'\''--B'\''--C'\'' topic
             /
    D---E---F---G master
'

. git-sh-setup

unset newbase
while case "$#" in 0) break ;; esac
do
	case "$1" in
	--onto)
		test 2 -le "$#" || usage
		newbase="$2"
		shift
		;;
	-*)
		usage
		;;
	*)
		break
		;;
	esac
	shift
done

# Make sure we do not have .dotest
if mkdir .dotest
then
	rmdir .dotest
else
	echo >&2 '
It seems that I cannot create a .dotest directory, and I wonder if you
are in the middle of patch application or another rebase.  If that is not
the case, please rm -fr .dotest and run me again.  I am stopping in case
you still have something valuable there.'
	exit 1
fi

# The tree must be really really clean.
git-update-index --refresh || exit
diff=$(git-diff-index --cached --name-status -r HEAD)
case "$diff" in
?*)	echo "$diff"
	exit 1
	;;
esac

# The upstream head must be given.  Make sure it is valid.
upstream_name="$1"
upstream=`git rev-parse --verify "${upstream_name}^0"` ||
    die "invalid upstream $upstream_name"

# If a hook exists, give it a chance to interrupt
if test -x "$GIT_DIR/hooks/pre-rebase"
then
	"$GIT_DIR/hooks/pre-rebase" ${1+"$@"} || {
		echo >&2 "The pre-rebase hook refused to rebase."
		exit 1
	}
fi

# If the branch to rebase is given, first switch to it.
case "$#" in
2)
	branch_name="$2"
	git-checkout "$2" || usage
	;;
*)
	branch_name=`git symbolic-ref HEAD` || die "No current branch"
	branch_name=`expr "z$branch_name" : 'zrefs/heads/\(.*\)'`
	;;
esac
branch=$(git-rev-parse --verify "${branch_name}^0") || exit

# Make sure the branch to rebase onto is valid.
onto_name=${newbase-"$upstream_name"}
onto=$(git-rev-parse --verify "${onto_name}^0") || exit

# Now we are rebasing commits $upstream..$branch on top of $onto

# Check if we are already based on $onto, but this should be
# done only when upstream and onto are the same.
if test "$upstream" = "onto"
then
	mb=$(git-merge-base "$onto" "$branch")
	if test "$mb" = "$onto"
	then
		echo >&2 "Current branch $branch_name is up to date."
		exit 0
	fi
fi

# Rewind the head to "$onto"; this saves our current head in ORIG_HEAD.
git-reset --hard "$onto"

# If the $onto is a proper descendant of the tip of the branch, then
# we just fast forwarded.
if test "$mb" = "$onto"
then
	echo >&2 "Fast-forwarded $branch to $newbase."
	exit 0
fi

git-format-patch -k --stdout --full-index "$upstream" ORIG_HEAD |
git am --binary -3 -k