CreateChange: Do not fail with ISE if base commit doesn't exist

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: If2886342815234d385e10d7ba7fe27127229ad4a

javatests/com/google/gerrit/acceptance/rest/change/CreateChangeIT.java

@@ -277,6 +277,16 @@ public class CreateChangeIT extends AbstractDaemonTest {
         input, UnprocessableEntityException.class, "Base notasha1 doesn't represent a valid SHA-1");
   }
 
+  @Test
+  public void createChangeWithNonExistingParentCommitFails() throws Exception {
+    ChangeInput input = newChangeInput(ChangeStatus.NEW);
+    input.baseCommit = "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef";
+    assertCreateFails(
+        input,
+        UnprocessableEntityException.class,
+        String.format("Base %s doesn't exist", input.baseCommit));
+  }
+
   @Test
   public void createChangeWithParentCommitOnWrongBranchFails() throws Exception {
     Map<String, PushOneCommit.Result> setup =