BranchApi: Add method to get the branch's reflog

GetReflog uses Repository#getReflogReader, but this is not implemented
by DfsRepository which is used in the test framework. As a result, calls
to this API method from tests results in UnsupportedOperationException.

Modify GetReflog to catch the UOE and rethrow as MethodNotAllowed, so
we get a graceful failure rather than "internal server error".

In the tests, expect MethodNotAllowed, with a TODO to rework when/if
the implementation of getReflogReader is done in DfsRepository.

Change-Id: I0d0d718ca4e4ecf2c544ea6e912397c20e2fd7e3

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/change/ChangeIT.java

@@ -160,6 +160,16 @@ public class ChangeIT extends AbstractDaemonTest {
     System.setProperty("user.timezone", systemTimeZone);
   }
 
+  @Test
+  public void reflog() throws Exception {
+    // Tests are using DfsRepository which does not implement getReflogReader,
+    // so this will always fail.
+    // TODO: change this if/when DfsRepository#getReflogReader is implemented.
+    exception.expect(MethodNotAllowedException.class);
+    exception.expectMessage("reflog not supported");
+    gApi.projects().name(project.get()).branch("master").reflog();
+  }
+
   @Test
   public void get() throws Exception {
     PushOneCommit.Result r = createChange();

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/projects/BranchApi.java

@@ -17,6 +17,7 @@ package com.google.gerrit.extensions.api.projects;
 import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.NotImplementedException;
 import com.google.gerrit.extensions.restapi.RestApiException;
+import java.util.List;
 
 public interface BranchApi {
   BranchApi create(BranchInput in) throws RestApiException;
@@ -28,6 +29,8 @@ public interface BranchApi {
   /** Returns the content of a file from the HEAD revision. */
   BinaryResult file(String path) throws RestApiException;
 
+  List<ReflogEntryInfo> reflog() throws RestApiException;
+
   /**
    * A default implementation which allows source compatibility when adding new methods to the
    * interface.
@@ -52,5 +55,10 @@ public interface BranchApi {
     public BinaryResult file(String path) throws RestApiException {
       throw new NotImplementedException();
     }
+
+    @Override
+    public List<ReflogEntryInfo> reflog() {
+      throw new NotImplementedException();
+    }
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/api/projects/BranchApiImpl.java

@@ -17,6 +17,7 @@ package com.google.gerrit.server.api.projects;
 import com.google.gerrit.extensions.api.projects.BranchApi;
 import com.google.gerrit.extensions.api.projects.BranchInfo;
 import com.google.gerrit.extensions.api.projects.BranchInput;
+import com.google.gerrit.extensions.api.projects.ReflogEntryInfo;
 import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.IdString;
 import com.google.gerrit.extensions.restapi.RestApiException;
@@ -27,11 +28,13 @@ import com.google.gerrit.server.project.DeleteBranch;
 import com.google.gerrit.server.project.FileResource;
 import com.google.gerrit.server.project.FilesCollection;
 import com.google.gerrit.server.project.GetContent;
+import com.google.gerrit.server.project.GetReflog;
 import com.google.gerrit.server.project.ProjectResource;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.assistedinject.Assisted;
 import java.io.IOException;
+import java.util.List;
 
 public class BranchApiImpl implements BranchApi {
   interface Factory {
@@ -43,6 +46,7 @@ public class BranchApiImpl implements BranchApi {
   private final DeleteBranch deleteBranch;
   private final FilesCollection filesCollection;
   private final GetContent getContent;
+  private final GetReflog getReflog;
   private final String ref;
   private final ProjectResource project;
 
@@ -53,6 +57,7 @@ public class BranchApiImpl implements BranchApi {
       DeleteBranch deleteBranch,
       FilesCollection filesCollection,
       GetContent getContent,
+      GetReflog getReflog,
       @Assisted ProjectResource project,
       @Assisted String ref) {
     this.branches = branches;
@@ -60,6 +65,7 @@ public class BranchApiImpl implements BranchApi {
     this.deleteBranch = deleteBranch;
     this.filesCollection = filesCollection;
     this.getContent = getContent;
+    this.getReflog = getReflog;
     this.project = project;
     this.ref = ref;
   }
@@ -102,6 +108,15 @@ public class BranchApiImpl implements BranchApi {
     }
   }
 
+  @Override
+  public List<ReflogEntryInfo> reflog() throws RestApiException {
+    try {
+      return getReflog.apply(resource());
+    } catch (IOException e) {
+      throw new RestApiException("Cannot retrieve reflog", e);
+    }
+  }
+
   private BranchResource resource() throws RestApiException, IOException {
     return branches.parse(project, IdString.fromDecoded(ref));
   }

gerrit-server/src/main/java/com/google/gerrit/server/project/GetReflog.java

@@ -17,7 +17,9 @@ package com.google.gerrit.server.project;
 import com.google.common.collect.Lists;
 import com.google.gerrit.extensions.api.projects.ReflogEntryInfo;
 import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.MethodNotAllowedException;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.server.CommonConverters;
 import com.google.gerrit.server.args4j.TimestampHandler;
@@ -27,13 +29,16 @@ import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.ArrayList;
 import java.util.List;
-import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.lib.ReflogEntry;
 import org.eclipse.jgit.lib.ReflogReader;
 import org.eclipse.jgit.lib.Repository;
 import org.kohsuke.args4j.Option;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class GetReflog implements RestReadView<BranchResource> {
+  private static final Logger log = LoggerFactory.getLogger(GetReflog.class);
+
   private final GitRepositoryManager repoManager;
 
   @Option(
@@ -80,14 +85,20 @@ public class GetReflog implements RestReadView<BranchResource> {
   }
 
   @Override
-  public List<ReflogEntryInfo> apply(BranchResource rsrc)
+  public List<ReflogEntryInfo> apply(BranchResource rsrc) throws RestApiException, IOException {
-      throws AuthException, ResourceNotFoundException, RepositoryNotFoundException, IOException {
     if (!rsrc.getControl().isOwner()) {
       throw new AuthException("not project owner");
     }
 
     try (Repository repo = repoManager.openRepository(rsrc.getNameKey())) {
-      ReflogReader r = repo.getReflogReader(rsrc.getRef());
+      ReflogReader r;
+      try {
+        r = repo.getReflogReader(rsrc.getRef());
+      } catch (UnsupportedOperationException e) {
+        String msg = "reflog not supported on repo " + rsrc.getNameKey().get();
+        log.error(msg);
+        throw new MethodNotAllowedException(msg);
+      }
       if (r == null) {
         throw new ResourceNotFoundException(rsrc.getRef());
       }