Log any failures while creating patch set refs

Some users have noticed failure cases where the ref isn't being
created for a patch set, and the pack file the objects are
supposed to be in is also not present in the repository after
the upload.  I haven't yet tracked down why this happens only
some of the time, but I did identify these call sites weren't
doing any error checking for unexpected return values.

We should always be getting a NEW result here, as the ref must
not exist locally and must be created successfully.  Any other
return value indicates the ref didn't create as we expected it
to, which means the repository isn't in the state it should be
either before we started, or after we finished this operation.

Signed-off-by: Shawn O. Pearce <sop@google.com>

src/main/java/com/google/gerrit/server/ssh/Receive.java

@@ -652,7 +652,10 @@ class Receive extends AbstractGitCommand {
     ru.setNewObjectId(c);
     ru.setRefLogIdent(refLogIdent);
     ru.setRefLogMessage("uploaded", false);
-    ru.update(walk);
+    if (ru.update(walk) != RefUpdate.Result.NEW) {
+      throw new IOException("Failed to create ref " + ps.getRefName() + " in "
+          + repo.getDirectory() + ": " + ru.getResult());
+    }
     PushQueue.scheduleUpdate(proj.getNameKey(), ru.getName());
 
     allNewChanges.add(change.getId());
@@ -825,7 +828,10 @@ class Receive extends AbstractGitCommand {
       ru.setNewObjectId(c);
       ru.setRefLogIdent(refLogIdent);
       ru.setRefLogMessage("uploaded", false);
-      ru.update(rp.getRevWalk());
+      if (ru.update(rp.getRevWalk()) != RefUpdate.Result.NEW) {
+        throw new IOException("Failed to create ref " + ps.getRefName()
+            + " in " + repo.getDirectory() + ": " + ru.getResult());
+      }
       PushQueue.scheduleUpdate(proj.getNameKey(), ru.getName());
       cmd.setResult(ReceiveCommand.Result.OK);