InlineEdit: Allow to upload change edit with git push

Edits can already be pulled with download commands. This change allows
edit to be pushed to gerrit by using magic branch %edit option.

Change must already exist for edit to be created/replaced. One use case
where edit might need to be replaced with git operations is rebasing of
edits on new patch set, in which case two refs are affected: old ref is
deleted and new ref is created:

  $ git push g HEAD:refs/for/master%e
  Counting objects: 14, done.
  [...]
  remote: Processing changes: updated: 1, refs: 2, done
  remote:
  remote: Updated Changes:
  remote:   http://localhost:8080/42 Fix typo in the doc [EDIT]

Change-Id: I3dbf66f1700c212ab90acfa77a5bd1e774b94555

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/git/AbstractPushForReview.java

@@ -23,6 +23,7 @@ import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.common.EditInfo;
 import com.google.gerrit.extensions.common.LabelInfo;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.reviewdb.client.Change;
@@ -162,6 +163,21 @@ public abstract class AbstractPushForReview extends AbstractDaemonTest {
     r.assertChange(Change.Status.DRAFT, null);
   }
 
+  @Test
+  public void testPushForMasterAsEdit() throws GitAPIException,
+      IOException, RestApiException {
+    PushOneCommit.Result r = pushTo("refs/for/master");
+    r.assertOkStatus();
+    EditInfo edit = getEdit(r.getChangeId());
+    assertThat(edit).isNull();
+
+    // specify edit as option
+    r = amendChange(r.getChangeId(), "refs/for/master%edit");
+    r.assertOkStatus();
+    edit = getEdit(r.getChangeId());
+    assertThat(edit).isNotNull();
+  }
+
   @Test
   public void testPushForMasterWithApprovals() throws GitAPIException,
       IOException, RestApiException {