Use dedicated endpoint for commit message retrieval for revisions

Instead of using GET /changes/<number>/edit:message for both edits and
normal revisions, differentiate on the client side and use dedicated
endpoints.

Change-Id: I7e9786c0b828cca9b0aa76bab43f10d223334d86

Documentation/rest-api-changes.txt

@@ -1462,8 +1462,7 @@ Retrieves content MIME type of a file from a change edit.
 'GET /changes/link:#change-id[\{change-id\}]/edit:message
 --
 
-Retrieves commit message from change edit or from current patch set when
-change edit doesn't exist.
+Retrieves commit message from change edit.
 
 .Request
 ----

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/edit/ChangeEditIT.java

@@ -275,11 +275,19 @@ public class ChangeEditIT extends AbstractDaemonTest {
 
   @Test
   public void updateMessageRest() throws Exception {
+    assertThat(adminSession.get(urlEditMessage()).getStatusCode())
+        .isEqualTo(SC_NOT_FOUND);
     EditMessage.Input in = new EditMessage.Input();
     in.message = String.format("New commit message\n\nChange-Id: %s",
         change.getKey());
     assertThat(adminSession.put(urlEditMessage(), in).getStatusCode())
         .isEqualTo(SC_NO_CONTENT);
+    RestResponse r = adminSession.get(urlEditMessage());
+    assertThat(adminSession.get(urlEditMessage()).getStatusCode())
+        .isEqualTo(SC_OK);
+    String content = r.getEntityContent();
+    assertThat(StringUtils.newStringUtf8(Base64.decodeBase64(content)))
+        .isEqualTo(in.message);
     Optional<ChangeEdit> edit = editUtil.byChange(change);
     assertThat(edit.get().getEditCommit().getFullMessage())
         .isEqualTo(in.message);

gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeFileApi.java

@@ -77,23 +77,16 @@ public class ChangeFileApi {
         });
   }
 
-  /** Get commit message in a PatchSet or change edit. */
-  public static void getMessage(PatchSet.Id id, AsyncCallback<String> cb) {
-    ChangeApi.change(id.getParentKey().get()).view("edit:message").get(
-        wrapper(cb));
-  }
-
   /**
    * Get the contents of a file or commit message in a PatchSet or change
    * edit.
    **/
   public static void getContentOrMessage(PatchSet.Id id, String path,
       AsyncCallback<String> cb) {
-    if (Patch.COMMIT_MSG.equals(path)) {
-      getMessage(id, cb);
-    } else {
-      contentEditOrPs(id, path).get(wrapper(cb));
-    }
+    RestApi api = (Patch.COMMIT_MSG.equals(path) && id.get() == 0)
+        ? messageEdit(id)
+        : contentEditOrPs(id, path);
+    api.get(wrapper(cb));
   }
 
   /** Put contents into a File in a change edit. */
@@ -145,6 +138,10 @@ public class ChangeFileApi {
         : ChangeApi.revision(id).view("files").id(filename).view("content");
   }
 
+  private static RestApi messageEdit(PatchSet.Id id) {
+    return ChangeApi.change(id.getParentKey().get()).view("edit:message");
+  }
+
   private static RestApi contentTypeEditOrPs(PatchSet.Id id, String filename) {
     return id.get() == 0
         ? contentEdit(id.getParentKey(), filename).view("type")

gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeEdits.java

@@ -39,7 +39,6 @@ import com.google.gerrit.extensions.restapi.RestView;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.server.ReviewDb;
-import com.google.gerrit.server.ChangeUtil;
 import com.google.gerrit.server.edit.ChangeEdit;
 import com.google.gerrit.server.edit.ChangeEditJson;
 import com.google.gerrit.server.edit.ChangeEditModifier;
@@ -47,7 +46,6 @@ import com.google.gerrit.server.edit.ChangeEditUtil;
 import com.google.gerrit.server.edit.UnchangedCommitMessageException;
 import com.google.gerrit.server.patch.PatchListNotAvailableException;
 import com.google.gerrit.server.project.InvalidChangeOperationException;
-import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
@@ -492,28 +490,22 @@ public class ChangeEdits implements
 
   @Singleton
   public static class GetMessage implements RestReadView<ChangeResource> {
-    private final ChangeUtil changeUtil;
     private final ChangeEditUtil editUtil;
 
     @Inject
-    GetMessage(ChangeUtil changeUtil,
-        ChangeEditUtil editUtil) {
-      this.changeUtil = changeUtil;
+    GetMessage(ChangeEditUtil editUtil) {
       this.editUtil = editUtil;
     }
 
     @Override
-    public BinaryResult apply(ChangeResource rsrc) throws AuthException, IOException,
-       OrmException, NoSuchChangeException {
+    public BinaryResult apply(ChangeResource rsrc) throws AuthException,
+        IOException, ResourceNotFoundException {
       Optional<ChangeEdit> edit = editUtil.byChange(rsrc.getChange());
-      // TODO(davido): Clean this up by returning 404 when edit doesn't exist.
-      // Client should call GET /changes/{id}/revisions/current/commit in this
-      // case; or, to be consistent with GET content logic, the client could
-      // call directly the right endpoint.
-      String m = edit.isPresent()
-        ? edit.get().getEditCommit().getFullMessage()
-        : changeUtil.getMessage(rsrc.getChange());
-      return BinaryResult.create(m).base64();
+      if (edit.isPresent()) {
+        return BinaryResult.create(
+            edit.get().getEditCommit().getFullMessage()).base64();
+      }
+      throw new ResourceNotFoundException();
     }
   }