Add REST endpoint to get the reflog of a branch

Change-Id: I9c0b3fa430b46762774bfa43710c3bb01fd2799e
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

Documentation/rest-api-projects.txt

@@ -761,6 +761,77 @@ The content is returned as base64 encoded string.
   Ly8gQ29weXJpZ2h0IChDKSAyMDEwIFRoZSBBbmRyb2lkIE9wZW4gU291cmNlIFByb2plY...
 ----
 
+[[get-reflog]]
+=== Get Reflog
+--
+'GET /projects/link:#project-name[\{project-name\}]/branches/link:#branch-id[\{branch-id\}]/reflog'
+--
+
+Gets the reflog of a certain branch.
+
+The caller must be project owner.
+
+.Request
+----
+  GET /projects/gerrit/branches/master/reflog HTTP/1.0
+----
+
+As response a list of link:#reflog-entry-info[ReflogEntryInfo] entities
+is returned that describe the reflog entries. The reflog entries are
+returned in reverse order.
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json;charset=UTF-8
+
+  )]}'
+  [
+    {
+      "old_id": "976ced8f4fc0909d7e1584d18455299545881d60",
+      "new_id": "2eaa94bac536654eb592c941e33b91f925698d16",
+      "who": {
+        "name": "Jane Roe",
+        "email": "jane.roe@example.com",
+        "date": "2014-06-30 11:53:43.000000000",
+        "tz": 120
+      },
+      "comment": "merged: fast forward"
+    },
+    {
+      "old_id": "c271c6a7161b74f85560c5899c8c73ee89ca5e29",
+      "new_id": "976ced8f4fc0909d7e1584d18455299545881d60",
+      "who": {
+        "name": "John Doe",
+        "email": "john.doe@example.com",
+        "date": "2013-10-02 10:45:26.000000000",
+        "tz": 120
+      },
+      "comment": "merged: fast forward"
+    },
+    {
+      "old_id": "0000000000000000000000000000000000000000",
+      "new_id": "c271c6a7161b74f85560c5899c8c73ee89ca5e29",
+      "who": {
+        "name": "John Doe",
+        "email": "john.doe@example.com",
+        "date": "2013-09-30 19:08:44.000000000",
+        "tz": 120
+      },
+      "comment": ""
+    }
+  ]
+----
+
+The get reflog endpoint also accepts a limit integer in the `n`
+parameter. This limits the results to show the last `n` reflog entries.
+
+Query the last 25 reflog entries.
+----
+  GET /projects/gerrit/branches/master/reflog?n=25 HTTP/1.0
+----
+
 [[child-project-endpoints]]
 == Child Project Endpoints
 
@@ -1554,6 +1625,21 @@ Message that should be used to commit the change of the project parent
 in the `project.config` file to the `refs/meta/config` branch.
 |=============================
 
+[[reflog-entry-info]]
+=== ReflogEntryInfo
+The `ReflogEntryInfo` entity describes an entry in a reflog.
+
+[options="header",width="50%",cols="1,6"]
+|============================
+|Field Name      |Description
+|`old_id`        |The old commit ID.
+|`new_id`        |The new commit ID.
+|`who`           |
+The user performing the change as a
+link:rest-api-changes.html#git-person-info[GitPersonInfo] entity.
+|`comment`       |Comment of the reflog entry.
+|============================
+
 [[repository-statistics-info]]
 === RepositoryStatisticsInfo
 The `RepositoryStatisticsInfo` entity contains information about

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

@@ -0,0 +1,99 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.project;
+
+import com.google.common.base.Function;
+import com.google.common.collect.Lists;
+import com.google.gerrit.extensions.common.GitPerson;
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.inject.Inject;
+
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.ReflogEntry;
+import org.eclipse.jgit.lib.ReflogReader;
+import org.eclipse.jgit.lib.Repository;
+import org.kohsuke.args4j.Option;
+
+import java.io.IOException;
+import java.sql.Timestamp;
+import java.util.List;
+
+public class GetReflog implements RestReadView<BranchResource> {
+  private final GitRepositoryManager repoManager;
+
+  @Option(name = "--limit", aliases = {"-n"}, metaVar = "CNT",
+      usage = "maximum number of reflog entries to list")
+  public GetReflog setLimit(int limit) {
+    this.limit = limit;
+    return this;
+  }
+
+  private int limit;
+
+  @Inject
+  public GetReflog(GitRepositoryManager repoManager) {
+    this.repoManager = repoManager;
+  }
+
+  @Override
+  public List<ReflogEntryInfo> apply(BranchResource rsrc) throws AuthException,
+      ResourceNotFoundException, RepositoryNotFoundException, IOException {
+    if (!rsrc.getControl().isOwner()) {
+      throw new AuthException("no project owner");
+    }
+
+    Repository repo = repoManager.openRepository(rsrc.getNameKey());
+    try {
+      ReflogReader r = repo.getReflogReader(rsrc.getRef());
+      if (r == null) {
+        throw new ResourceNotFoundException(rsrc.getRef());
+      }
+      List<ReflogEntry> entries =
+          limit > 0 ? r.getReverseEntries(limit) : r.getReverseEntries();
+      return Lists.transform(entries, new Function<ReflogEntry, ReflogEntryInfo>() {
+        @Override
+        public ReflogEntryInfo apply(ReflogEntry e) {
+          return new ReflogEntryInfo(e);
+        }});
+    } finally {
+      repo.close();
+    }
+  }
+
+  public static class ReflogEntryInfo {
+    public String oldId;
+    public String newId;
+    public GitPerson who;
+    public String comment;
+
+    public ReflogEntryInfo(ReflogEntry e) {
+      oldId = e.getOldId().getName();
+      newId = e.getNewId().getName();
+
+      PersonIdent ident = e.getWho();
+      who = new GitPerson();
+      who.name = ident.getName();
+      who.email = ident.getEmailAddress();
+      who.date = new Timestamp(ident.getWhen().getTime());
+      who.tz = ident.getTimeZoneOffset();
+
+      comment = e.getComment();
+    }
+  }
+}

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

@@ -59,6 +59,7 @@ public class Module extends RestApiModule {
     get(BRANCH_KIND).to(GetBranch.class);
     delete(BRANCH_KIND).to(DeleteBranch.class);
     install(new FactoryModuleBuilder().build(CreateBranch.Factory.class));
+    get(BRANCH_KIND, "reflog").to(GetReflog.class);
     child(BRANCH_KIND, "files").to(FilesCollection.class);
     get(FILE_KIND, "content").to(GetContent.class);