Fix merge validator exception type is ignored

The switch case in updateChangeStatus was supposed to handle the failed
cases but it was never reached by changes who failed to merge, since
only the submitted ones are returned by the validation function.

Now, updateChangeStatus is called on every change that doesn't make it
out of the validation. Also, the parameter name 'submitted' did not make
sense since the method handles changes who cannot be submitted, so it is
renamed to 'changes'.

Also, destBranch is optionally null in updateChangeStatus since it
doesn't apply to failed merges.

Tests are modified since the error output is more verbose than before.

Bug: Issue 3741
Change-Id: Id1de81b3136b94e210c957a58b5c801a1faa3244

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/SubmitByMergeIfNecessaryIT.java

@@ -296,7 +296,9 @@ public class SubmitByMergeIfNecessaryIT extends AbstractSubmitByMerge {
         "a.txt", "1", "a-topic-here");
     approve(change3b.getChangeId());
 
-    submitWithConflict(change3a.getChangeId(), "Merge Conflict");
+    submitWithConflict(change3a.getChangeId(), "Cannot merge " +
+        change3a.getCommit().name() +
+        "\nMissing dependency");
 
     RevCommit tipbranch = getRemoteLog(project, "branch").get(0);
     assertThat(tipbranch.getShortMessage()).isEqualTo(

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/SubmitByRebaseIfNecessaryIT.java

@@ -107,7 +107,9 @@ public class SubmitByRebaseIfNecessaryIT extends AbstractSubmit {
     testRepo.reset(initialHead);
     PushOneCommit.Result change2 =
         createChange("Change 2", "a.txt", "other content");
-    submitWithConflict(change2.getChangeId(), "Merge Conflict");
+    submitWithConflict(change2.getChangeId(), "Cannot rebase " +
+        change2.getCommit().name() +
+        ": The change could not be rebased due to a conflict during merge.");
     RevCommit head = getRemoteHead();
     assertThat(head).isEqualTo(oldHead);
     assertCurrentRevision(change2.getChangeId(), 1, change2.getCommitId());

gerrit-server/src/main/java/com/google/gerrit/server/git/CommitMergeStatus.java

@@ -39,7 +39,7 @@ public enum CommitMergeStatus {
           + "Please rebase the change locally and upload the rebased commit for review."),
 
   /** */
-  MISSING_DEPENDENCY(""),
+  MISSING_DEPENDENCY("Missing dependency"),
 
   /** */
   NO_PATCH_SET(""),

gerrit-server/src/main/java/com/google/gerrit/server/git/MergeOp.java

@@ -380,7 +380,7 @@ public class MergeOp {
         integrateIntoHistory(cs, caller);
       } catch (IntegrationException e) {
         logError("Merge Conflict", e);
-        throw new ResourceConflictException("Merge Conflict", e);
+        throw new ResourceConflictException(e.getMessage());
       }
     } catch (IOException e) {
       // Anything before the merge attempt is an error
@@ -587,7 +587,8 @@ public class MergeOp {
 
   private ListMultimap<SubmitType, ChangeData> validateChangeList(
       Collection<ChangeData> submitted, IdentifiedUser caller)
-    throws IntegrationException {
+      throws IntegrationException, ResourceConflictException,
+      NoSuchChangeException, OrmException {
     logDebug("Validating {} changes", submitted.size());
     ListMultimap<SubmitType, ChangeData> toSubmit = ArrayListMultimap.create();
 
@@ -701,6 +702,11 @@ public class MergeOp {
       commit.add(canMergeFlag);
       toSubmit.put(submitType, cd);
     }
+
+    List<ChangeData> notSubmittable = new ArrayList<>(submitted);
+    notSubmittable.removeAll(toSubmit.values());
+    updateChangeStatus(notSubmittable, null, false, caller);
+
     logDebug("Submitting on this run: {}", toSubmit);
     return toSubmit;
   }
@@ -822,18 +828,18 @@ public class MergeOp {
     return "";
   }
 
-  private void updateChangeStatus(List<ChangeData> submitted,
+  private void updateChangeStatus(List<ChangeData> changes,
       Branch.NameKey destBranch, boolean dryRun, IdentifiedUser caller)
       throws NoSuchChangeException, IntegrationException, ResourceConflictException,
       OrmException {
     if (!dryRun) {
-      logDebug("Updating change status for {} changes", submitted.size());
+      logDebug("Updating change status for {} changes", changes.size());
     } else {
       logDebug("Checking change state for {} changes in a dry run",
-          submitted.size());
+          changes.size());
     }
-    MergeTip mergeTip = mergeTips.get(destBranch);
-    for (ChangeData cd : submitted) {
+    MergeTip mergeTip = destBranch != null ? mergeTips.get(destBranch) : null;
+    for (ChangeData cd : changes) {
       Change c = cd.change();
       CodeReviewCommit commit = commits.get(c.getId());
       CommitMergeStatus s = commit != null ? commit.getStatusCode() : null;