Create a draft patch set when a draft patch set is rebased

Currently rebasing a draft patch set will create a non-draft patch set
which is published. It is unexpected that rebasing a draft patch set
publishes the modifications done in the draft patch set.

Bug: issue 1558
Change-Id: Iaf3b2d5b34076fbd85958fffd4bb1369bc8fd6db
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/ChangeUtil.java b/gerrit-server/src/main/java/com/google/gerrit/server/ChangeUtil.java
index 94b2169..535ad8e 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/ChangeUtil.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/ChangeUtil.java
@@ -353,6 +353,7 @@
         newPatchSet.setCreatedOn(new Timestamp(System.currentTimeMillis()));
         newPatchSet.setUploader(user.getAccountId());
         newPatchSet.setRevision(new RevId(rebasedCommit.name()));
+        newPatchSet.setDraft(originalPatchSet.isDraft());
 
         final PatchSetInfo info =
             patchSetInfoFactory.get(rebasedCommit, newPatchSet.getId());