Execute Git commands with AccessPath.GIT

Since 53b0e7ffb5 ("Require branch deletion permission for pushes
over HTTP") branch deletion or creation over ssh:// by Git push
failed, because the AccessPath was specified wrong.  We need to
force a temporary change for the current command to AccessPath.GIT,
rather than the default of AccessPath.SSH_COMMAND.

Doing this is a bit ugly, as we have to build up a temporary
SshSession, and also a temporary SshScope.Context to point to that
temporary session.  Installing the temporary context before we call
the startThread method will ensure the background worker properly
inherits our context object, and therefore our identity as a Git
based command.

Change-Id: I6cfc91966fffa2c5054ae6d65f6ac57dc751a4fc
Signed-off-by: Shawn O. Pearce <sop@google.com>

gerrit-sshd/src/main/java/com/google/gerrit/sshd/AbstractGitCommand.java

@@ -0,0 +1,101 @@
+// Copyright (C) 2008 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.sshd;
+
+import com.google.gerrit.reviewdb.Project;
+import com.google.gerrit.server.AccessPath;
+import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.project.ProjectControl;
+import com.google.gerrit.sshd.SshScope.Context;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+import org.apache.sshd.server.Environment;
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
+import org.eclipse.jgit.lib.Repository;
+import org.kohsuke.args4j.Argument;
+
+import java.io.IOException;
+import java.net.SocketAddress;
+
+public abstract class AbstractGitCommand extends BaseCommand {
+  @Argument(index = 0, metaVar = "PROJECT.git", required = true, usage = "project name")
+  protected ProjectControl projectControl;
+
+  @Inject
+  private GitRepositoryManager repoManager;
+
+  @Inject
+  private SshSession session;
+
+  @Inject
+  private SshScope.Context context;
+
+  @Inject
+  private IdentifiedUser user;
+
+  @Inject
+  private IdentifiedUser.GenericFactory userFactory;
+
+  protected Repository repo;
+  protected Project project;
+
+  @Override
+  public void start(final Environment env) {
+    final Context ctx = new Context(newSession(), context.getCommandLine());
+    final Context old = SshScope.set(ctx);
+    try {
+      startThread(new CommandRunnable() {
+        @Override
+        public void run() throws Exception {
+          parseCommandLine();
+          AbstractGitCommand.this.service();
+        }
+      });
+    } finally {
+      SshScope.set(old);
+    }
+  }
+
+  private SshSession newSession() {
+    return new SshSession(session, session.getRemoteAddress(), userFactory
+        .create(AccessPath.GIT, new Provider<SocketAddress>() {
+          @Override
+          public SocketAddress get() {
+            return session.getRemoteAddress();
+          }
+        }, user.getAccountId()));
+  }
+
+  private void service() throws IOException, Failure {
+    project = projectControl.getProjectState().getProject();
+
+    final String name = project.getName();
+    try {
+      repo = repoManager.openRepository(name);
+    } catch (RepositoryNotFoundException e) {
+      throw new Failure(1, "fatal: '" + name + "': not a git archive", e);
+    }
+
+    try {
+      runImpl();
+    } finally {
+      repo.close();
+    }
+  }
+
+  protected abstract void runImpl() throws IOException, Failure;
+}