ConsistencyChecker: Handle dangling PS ref with expect_merged_as

If a direct push to a branch fails, it's possible to both create a new
patch set ref and update the branch, but fail the database write that
creates the new patch set record and updates the change's current
patch set. ConsistencyChecker was not able to fix up this case,
because the patch set ID it found in the refs did not match the
current patch set ID of the change. There was no reason for this other
than I didn't implement it. But we've seen these in the wild, so now
is the time to fix it.

This doesn't handle the general problem of dangling patch set refs
outside of the expect_merged_as path; fixing those is still possible,
but is not the proximate corruption issue we're trying to fix here.

Change-Id: I0c2082e45bd6090e0b2b9e024c2d32a7df603a66

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/server/change/ConsistencyCheckerIT.java

@@ -512,11 +512,11 @@ public class ConsistencyCheckerIT extends AbstractDaemonTest {
         ctl, fix,
         problem(
             "No patch set found for merged commit " + mergedAs.name(),
-            FIXED, "Inserted as patch set 2"),
+            FIXED, "Marked change as merged"),
         problem(
             "Expected merged commit " + mergedAs.name()
                 + " has no associated patch set",
-            FIXED, "Marked change as merged"));
+            FIXED, "Inserted as patch set 2"));
 
     ctl = reload(ctl);
     PatchSet.Id psId2 = new PatchSet.Id(ctl.getId(), 2);
@@ -553,11 +553,11 @@ public class ConsistencyCheckerIT extends AbstractDaemonTest {
         ctl, fix,
         problem(
             "No patch set found for merged commit " + mergedAs.name(),
-            FIXED, "Inserted as patch set 2"),
+            FIXED, "Marked change as merged"),
         problem(
             "Expected merged commit " + mergedAs.name()
                 + " has no associated patch set",
-            FIXED, "Marked change as merged"));
+            FIXED, "Inserted as patch set 2"));
 
     ctl = reload(ctl);
     PatchSet.Id psId2 = new PatchSet.Id(ctl.getId(), 2);
@@ -584,9 +584,106 @@ public class ConsistencyCheckerIT extends AbstractDaemonTest {
     assertProblems(
         ctl, fix,
         problem(
-            "Expected merged commit " + rev1 + " corresponds to patch set "
-                + ps1.getId() + ", which is not the current patch set "
-                + ps2.getId()));
+            "No patch set found for merged commit " + rev1,
+            FIXED, "Marked change as merged"),
+        problem(
+            "Expected merge commit " + rev1 + " corresponds to patch set 1,"
+                + " not the current patch set 2",
+            FIXED, "Deleted patch set"),
+        problem(
+            "Expected merge commit " + rev1 + " corresponds to patch set 1,"
+                + " not the current patch set 2",
+            FIXED, "Inserted as patch set 3"));
+
+    ctl = reload(ctl);
+    PatchSet.Id psId3 = new PatchSet.Id(ctl.getId(), 3);
+    assertThat(ctl.getChange().currentPatchSetId()).isEqualTo(psId3);
+    assertThat(ctl.getChange().getStatus()).isEqualTo(Change.Status.MERGED);
+    assertThat(psUtil.byChangeAsMap(db, ctl.getNotes()).keySet())
+        .containsExactly(ps2.getId(), psId3);
+    assertThat(psUtil.get(db, ctl.getNotes(), psId3).getRevision().get())
+        .isEqualTo(rev1);
+  }
+
+  @Test
+  public void expectedMergedCommitIsDanglingPatchSetOlderThanCurrent()
+      throws Exception {
+    ChangeControl ctl = insertChange();
+    PatchSet ps1 = psUtil.current(db, ctl.getNotes());
+
+    // Create dangling ref so next ID in the database becomes 3.
+    PatchSet.Id psId2 = new PatchSet.Id(ctl.getId(), 2);
+    RevCommit commit2 = patchSetCommit(psId2);
+    String rev2 = commit2.name();
+    testRepo.branch(psId2.toRefName()).update(commit2);
+
+    ctl = incrementPatchSet(ctl);
+    PatchSet ps3 = psUtil.current(db, ctl.getNotes());
+    assertThat(ps3.getId().get()).isEqualTo(3);
+
+    testRepo.branch(ctl.getChange().getDest().get())
+        .update(testRepo.getRevWalk().parseCommit(ObjectId.fromString(rev2)));
+
+    FixInput fix = new FixInput();
+    fix.expectMergedAs = rev2;
+    assertProblems(
+        ctl, fix,
+        problem(
+            "No patch set found for merged commit " + rev2,
+            FIXED, "Marked change as merged"),
+        problem(
+            "Expected merge commit " + rev2 + " corresponds to patch set 2,"
+                + " not the current patch set 3",
+            FIXED, "Deleted patch set"),
+        problem(
+            "Expected merge commit " + rev2 + " corresponds to patch set 2,"
+                + " not the current patch set 3",
+            FIXED, "Inserted as patch set 4"));
+
+    ctl = reload(ctl);
+    PatchSet.Id psId4 = new PatchSet.Id(ctl.getId(), 4);
+    assertThat(ctl.getChange().currentPatchSetId()).isEqualTo(psId4);
+    assertThat(ctl.getChange().getStatus()).isEqualTo(Change.Status.MERGED);
+    assertThat(psUtil.byChangeAsMap(db, ctl.getNotes()).keySet())
+        .containsExactly(ps1.getId(), ps3.getId(), psId4);
+    assertThat(psUtil.get(db, ctl.getNotes(), psId4).getRevision().get())
+        .isEqualTo(rev2);
+  }
+
+  @Test
+  public void expectedMergedCommitIsDanglingPatchSetNewerThanCurrent()
+      throws Exception {
+    ChangeControl ctl = insertChange();
+    PatchSet ps1 = psUtil.current(db, ctl.getNotes());
+
+    // Create dangling ref with no patch set.
+    PatchSet.Id psId2 = new PatchSet.Id(ctl.getId(), 2);
+    RevCommit commit2 = patchSetCommit(psId2);
+    String rev2 = commit2.name();
+    testRepo.branch(psId2.toRefName()).update(commit2);
+
+    testRepo.branch(ctl.getChange().getDest().get())
+        .update(testRepo.getRevWalk().parseCommit(ObjectId.fromString(rev2)));
+
+    FixInput fix = new FixInput();
+    fix.expectMergedAs = rev2;
+    assertProblems(
+        ctl, fix,
+        problem(
+            "No patch set found for merged commit " + rev2,
+            FIXED, "Marked change as merged"),
+        problem(
+            "Expected merge commit " + rev2 + " corresponds to patch set 2,"
+                + " not the current patch set 1",
+            FIXED, "Inserted as patch set 2"));
+
+    ctl = reload(ctl);
+    assertThat(ctl.getChange().currentPatchSetId()).isEqualTo(psId2);
+    assertThat(ctl.getChange().getStatus()).isEqualTo(Change.Status.MERGED);
+    assertThat(psUtil.byChangeAsMap(db, ctl.getNotes()).keySet())
+        .containsExactly(ps1.getId(), psId2);
+    assertThat(psUtil.get(db, ctl.getNotes(), psId2).getRevision().get())
+        .isEqualTo(rev2);
   }
 
   @Test
@@ -683,8 +780,9 @@ public class ConsistencyCheckerIT extends AbstractDaemonTest {
         db, ins.getChange(), userFactory.create(adminId));
   }
 
-  private PatchSet.Id nextPatchSetId(ChangeControl ctl) {
-    return ChangeUtil.nextPatchSetId(ctl.getChange().currentPatchSetId());
+  private PatchSet.Id nextPatchSetId(ChangeControl ctl) throws Exception {
+    return ChangeUtil.nextPatchSetId(
+        testRepo.getRepository(), ctl.getChange().currentPatchSetId());
   }
 
   private ChangeControl incrementPatchSet(ChangeControl ctl) throws Exception {