rebase: use peel_committish() where appropriate

The revisions specified on the command-line as <onto> and <upstream>
arguments could be of the form :/quuxery; so, use peel_committish() to
resolve them.  The failing tests in t/rebase and t/rebase-interactive
now pass.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase.sh

@@ -434,7 +434,7 @@ then
 		shift
 		;;
 	esac
-	upstream=`git rev-parse --verify "${upstream_name}^0"` ||
+	upstream=$(peel_committish "${upstream_name}") ||
 	die "$(eval_gettext "invalid upstream \$upstream_name")"
 	upstream_arg="$upstream_name"
 else
@@ -470,7 +470,7 @@ case "$onto_name" in
 	fi
 	;;
 *)
-	onto=$(git rev-parse --verify "${onto_name}^0") ||
+	onto=$(peel_committish "$onto_name") ||
 	die "$(eval_gettext "Does not point to a valid commit: \$onto_name")"
 	;;
 esac

t/t3400-rebase.sh

@@ -88,7 +88,7 @@ test_expect_success 'rebase fast-forward to master' '
 	test_i18ngrep "Fast-forwarded HEAD to my-topic-branch" out
 '
 
-test_expect_failure 'rebase, with <onto> and <upstream> specified as :/quuxery' '
+test_expect_success 'rebase, with <onto> and <upstream> specified as :/quuxery' '
 	test_when_finished "git branch -D torebase" &&
 	git checkout -b torebase my-topic-branch^ &&
 	upstream=$(git rev-parse ":/Add B") &&

t/t3404-rebase-interactive.sh

@@ -947,7 +947,7 @@ test_expect_success 'rebase -i respects core.commentchar' '
 	test B = $(git cat-file commit HEAD^ | sed -ne \$p)
 '
 
-test_expect_failure 'rebase -i, with <onto> and <upstream> specified as :/quuxery' '
+test_expect_success 'rebase -i, with <onto> and <upstream> specified as :/quuxery' '
 	test_when_finished "git branch -D torebase" &&
 	git checkout -b torebase branch1 &&
 	upstream=$(git rev-parse ":/J") &&