InlineEdit: Add REST endpoint to retrieve commit message

Change-Id: I9017df268614e8035513af173a7067a8aa10fcec

Documentation/rest-api-changes.txt

@@ -1369,6 +1369,30 @@ specified file was deleted in the change edit "`204 No Content`" is returned.
   RnJvbSA3ZGFkY2MxNTNmZGVhMTdhYTg0ZmYzMmE2ZTI0NWRiYjY...
 ----
 
+[[get-edit-message]]
+=== Retrieve commit message from Change Edit or current patch set of the change
+--
+'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.
+
+.Request
+----
+  GET /changes/myProject~master~I8473b95934b5732ac55d26311a706c9c2bde9940/edit:message HTTP/1.0
+----
+
+The commit message is returned as base64 encoded string.
+
+.Response
+----
+  HTTP/1.1 200 OK
+
+  VGhpcyBpcyBhIGNvbW1pdCBtZXNzYWdlCgpDaGFuZ2UtSWQ6IElhYzhmZGM1MGRlZjFiYWUzYjAz
+M2JhNjcxZTk0OTBmNzUxNDU5ZGUzCg==
+----
+
 [[publish-edit]]
 === Publish Change Edit
 --

gerrit-server/src/main/java/com/google/gerrit/server/ChangeUtil.java

@@ -450,6 +450,36 @@ public class ChangeUtil {
     }
   }
 
+  public String getMessage(Change change)
+      throws NoSuchChangeException, OrmException,
+      MissingObjectException, IncorrectObjectTypeException, IOException {
+    Change.Id changeId = change.getId();
+    PatchSet ps = db.get().patchSets().get(change.currentPatchSetId());
+    if (ps == null) {
+      throw new NoSuchChangeException(changeId);
+    }
+
+    Repository git;
+    try {
+      git = gitManager.openRepository(change.getProject());
+    } catch (RepositoryNotFoundException e) {
+      throw new NoSuchChangeException(changeId, e);
+    }
+    try {
+      RevWalk revWalk = new RevWalk(git);
+      try {
+        RevCommit commit =
+            revWalk.parseCommit(ObjectId.fromString(ps.getRevision()
+                .get()));
+        return commit.getFullMessage();
+      } finally {
+        revWalk.release();
+      }
+    } finally {
+      git.close();
+    }
+  }
+
   public void deleteDraftChange(Change change)
       throws NoSuchChangeException, OrmException, IOException {
     Change.Id changeId = change.getId();

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

@@ -24,6 +24,7 @@ import com.google.gerrit.extensions.restapi.AcceptsDelete;
 import com.google.gerrit.extensions.restapi.AcceptsPost;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.ChildCollection;
 import com.google.gerrit.extensions.restapi.DefaultInput;
 import com.google.gerrit.extensions.restapi.IdString;
@@ -38,12 +39,14 @@ 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;
 import com.google.gerrit.server.edit.ChangeEditUtil;
 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;
@@ -475,4 +478,31 @@ public class ChangeEdits implements
       return Response.none();
     }
   }
+
+  @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;
+      this.editUtil = editUtil;
+    }
+
+    @Override
+    public BinaryResult apply(ChangeResource rsrc) throws AuthException, IOException,
+       OrmException, NoSuchChangeException {
+      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();
+    }
+  }
 }

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

@@ -109,6 +109,7 @@ public class Module extends RestApiModule {
     child(CHANGE_KIND, "edit:publish").to(PublishChangeEdit.class);
     child(CHANGE_KIND, "edit:rebase").to(RebaseChangeEdit.class);
     put(CHANGE_KIND, "edit:message").to(ChangeEdits.EditMessage.class);
+    get(CHANGE_KIND, "edit:message").to(ChangeEdits.GetMessage.class);
     put(CHANGE_EDIT_KIND, "/").to(ChangeEdits.Put.class);
     delete(CHANGE_EDIT_KIND).to(ChangeEdits.DeleteContent.class);
     get(CHANGE_EDIT_KIND, "/").to(ChangeEdits.Get.class);