add simple tests of consistency across rebase types

Helped-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Martin von Zweigbergk <martinvonz@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/lib-rebase.sh b/t/lib-rebase.sh
index 6ccf797..1e0ff28 100644
--- a/t/lib-rebase.sh
+++ b/t/lib-rebase.sh
@@ -65,3 +65,19 @@
 	test_set_editor "$(pwd)/fake-editor.sh"
 	chmod a+x fake-editor.sh
 }
+
+# checks that the revisions in "$2" represent a linear range with the
+# subjects in "$1"
+test_linear_range () {
+	revlist_merges=$(git rev-list --merges "$2") &&
+	test -z "$revlist_merges" &&
+	expected=$1
+	set -- $(git log --reverse --format=%s "$2")
+	test "$expected" = "$*"
+}
+
+reset_rebase () {
+	test_might_fail git rebase --abort &&
+	git reset --hard &&
+	git clean -f
+}