Implement new /changes/{id}/action style REST API

All existing JSON APIs are converted to this new style.

/changes/{id} parses the id field from a JSON response from a prior
response and uses that to uniquely identify a change and verify the
caller can see it. If the user requests only /changes/{id}/ then the
data is returned as a single JSON object.

This commit also gives full remote control of plugins using the
/plugins/ namespace:

  PUT /plugins/{name}    (JAR as request body)
  POST /plugins/{name}   (JSON object {url:"https://..."})
  DELETE /plugins/{name}
  GET /plugins/{name}/gerrit~status
  POST /plugins/{name}/gerrit~reload
  POST /plugins/{name}/gerrit~enable
  POST /plugins/{name}/gerrit~disable

The commit provides some project admin commands:

  GET /projects/{name}/description
  PUT /projects/{name}/description

  GET /projects/{name}/parent
  PUT /projects/{name}/parent

Project dashboards have moved:

  GET /projects/{name}/dashboards
  GET /projects/{name}/dashboards/{id}
  GET /projects/{name}/dashboards/default

To access project names containing /, the name must be encoded with
URL encoding, translating / to %2F.

Change-Id: I6a38902ee473003ec637758b7c911f926a2e948a

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

@@ -0,0 +1,140 @@
+// Copyright (C) 2012 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.change;
+
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.TopLevelResource;
+import com.google.gerrit.extensions.restapi.RestCollection;
+import com.google.gerrit.extensions.restapi.RestView;
+import com.google.gerrit.reviewdb.client.Branch;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.project.ChangeControl;
+import com.google.gerrit.server.project.NoSuchChangeException;
+import com.google.gerrit.server.query.change.QueryChanges;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+import org.eclipse.jgit.lib.Constants;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLDecoder;
+import java.util.Collections;
+import java.util.List;
+
+public class ChangesCollection implements
+    RestCollection<TopLevelResource, ChangeResource> {
+  private final Provider<ReviewDb> db;
+  private final ChangeControl.Factory changeControlFactory;
+  private final Provider<QueryChanges> queryFactory;
+  private final DynamicMap<RestView<ChangeResource>> views;
+
+  @Inject
+  ChangesCollection(
+      Provider<ReviewDb> dbProvider,
+      ChangeControl.Factory changeControlFactory,
+      Provider<QueryChanges> queryFactory,
+      DynamicMap<RestView<ChangeResource>> views) {
+    this.db = dbProvider;
+    this.changeControlFactory = changeControlFactory;
+    this.queryFactory = queryFactory;
+    this.views = views;
+  }
+
+  @Override
+  public RestView<TopLevelResource> list() {
+    return queryFactory.get();
+  }
+
+  @Override
+  public DynamicMap<RestView<ChangeResource>> views() {
+    return views;
+  }
+
+  @Override
+  public ChangeResource parse(TopLevelResource root, String id)
+      throws ResourceNotFoundException, OrmException,
+      UnsupportedEncodingException {
+    ParsedId p = new ParsedId(id);
+    List<Change> changes = findChanges(p);
+    if (changes.size() != 1) {
+      throw new ResourceNotFoundException(id);
+    }
+
+    ChangeControl control;
+    try {
+      control = changeControlFactory.validateFor(changes.get(0));
+    } catch (NoSuchChangeException e) {
+      throw new ResourceNotFoundException(id);
+    }
+    return new ChangeResource(control);
+  }
+
+  private List<Change> findChanges(ParsedId k) throws OrmException {
+    if (k.legacyId != null) {
+      Change c = db.get().changes().get(k.legacyId);
+      if (c != null) {
+        return ImmutableList.of(c);
+      }
+      return Collections.emptyList();
+    } else if (k.project == null && k.branch == null && k.changeId != null) {
+      return db.get().changes().byKey(new Change.Key(k.changeId)).toList();
+    }
+    return db.get().changes().byBranchKey(
+        k.branch(),
+        new Change.Key(k.changeId)).toList();
+  }
+
+  private static class ParsedId {
+    Change.Id legacyId;
+    String project;
+    String branch;
+    String changeId;
+
+    ParsedId(String id) throws ResourceNotFoundException,
+        UnsupportedEncodingException {
+      if (id.matches("^[0-9]+$")) {
+        legacyId = Change.Id.parse(id);
+        return;
+      }
+
+      int t2 = id.lastIndexOf('~');
+      int t1 = id.lastIndexOf('~', t2 - 1);
+      if (t1 < 0 || t2 < 0) {
+        if (!id.matches("^I[0-9a-z]{40}$")) {
+          throw new ResourceNotFoundException(id);
+        }
+        changeId = id;
+        return;
+      }
+
+      project = URLDecoder.decode(id.substring(0, t1), "UTF-8");
+      branch = URLDecoder.decode(id.substring(t1 + 1, t2), "UTF-8");
+      changeId = URLDecoder.decode(id.substring(t2 + 1), "UTF-8");
+
+      if (!branch.startsWith(Constants.R_REFS)) {
+        branch = Constants.R_HEADS + branch;
+      }
+    }
+
+    Branch.NameKey branch() {
+      return new Branch.NameKey(new Project.NameKey(project), branch);
+    }
+  }
+}