Enable aliases for SSH commands

Site administrators can alias SSH commands from a plugin into the
gerrit namespace using the ssh-alias section in gerrit.config:

  [ssh-alias]
    ls = gerrit ls-projects
    replicate = replication start

The aliases are configured statically at server startup, but are
resolved dynamically at invocation time to the currently loaded
version of the plugin. If the plugin is not loaded, or does not
define the command, "not found" is returned to the user.

Change-Id: Ie98edbef6c8f2fcb3960e7f06329f5dee670ac1e

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

@@ -16,6 +16,7 @@ package com.google.gerrit.sshd;
 
 import static com.google.inject.Scopes.SINGLETON;
 
+import com.google.common.collect.Maps;
 import com.google.gerrit.lifecycle.LifecycleModule;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.AccountGroup;
@@ -29,6 +30,7 @@ import com.google.gerrit.server.account.AccountManager;
 import com.google.gerrit.server.account.ChangeUserName;
 import com.google.gerrit.server.config.FactoryModule;
 import com.google.gerrit.server.config.GerritRequestModule;
+import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.git.QueueProvider;
 import com.google.gerrit.server.git.WorkQueue;
 import com.google.gerrit.server.plugins.ModuleGenerator;
@@ -49,19 +51,32 @@ import com.google.gerrit.sshd.commands.DefaultCommandModule;
 import com.google.gerrit.sshd.commands.QueryShell;
 import com.google.gerrit.util.cli.CmdLineParser;
 import com.google.gerrit.util.cli.OptionHandlerUtil;
+import com.google.inject.Inject;
 import com.google.inject.internal.UniqueAnnotations;
 import com.google.inject.servlet.RequestScoped;
 
 import org.apache.sshd.common.KeyPairProvider;
 import org.apache.sshd.server.CommandFactory;
 import org.apache.sshd.server.PublickeyAuthenticator;
+import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ObjectId;
 import org.kohsuke.args4j.spi.OptionHandler;
 
 import java.net.SocketAddress;
+import java.util.Map;
 
 /** Configures standard dependencies for {@link SshDaemon}. */
 public class SshModule extends FactoryModule {
+  private final Map<String, String> aliases;
+
+  @Inject
+  SshModule(@GerritServerConfig Config cfg) {
+    aliases = Maps.newHashMap();
+    for (String name : cfg.getNames("ssh-alias")) {
+      aliases.put(name, cfg.getString("ssh-alias", null, name));
+    }
+  }
+
   @Override
   protected void configure() {
     bindScope(RequestScoped.class, SshScope.REQUEST);
@@ -69,6 +84,7 @@ public class SshModule extends FactoryModule {
 
     configureRequestScope();
     configureCmdLineParser();
+    configureAliases();
 
     install(SshKeyCacheImpl.module());
     bind(SshLog.class);
@@ -78,7 +94,7 @@ public class SshModule extends FactoryModule {
     factory(PeerDaemonUser.Factory.class);
 
     bind(DispatchCommandProvider.class).annotatedWith(Commands.CMD_ROOT)
-        .toInstance(new DispatchCommandProvider("", Commands.CMD_ROOT));
+        .toInstance(new DispatchCommandProvider(Commands.CMD_ROOT));
     bind(CommandFactoryProvider.class);
     bind(CommandFactory.class).toProvider(CommandFactoryProvider.class);
     bind(WorkQueue.Executor.class).annotatedWith(StreamCommandExecutor.class)
@@ -111,6 +127,20 @@ public class SshModule extends FactoryModule {
     });
   }
 
+  private void configureAliases() {
+    CommandName gerrit = Commands.named("gerrit");
+    for (Map.Entry<String, String> e : aliases.entrySet()) {
+      String name = e.getKey();
+      String[] dest = e.getValue().split("[ \\t]+");
+      CommandName cmd = Commands.named(dest[0]);
+      for (int i = 1; i < dest.length; i++) {
+        cmd = Commands.named(cmd, dest[i]);
+      }
+      bind(Commands.key(gerrit, name))
+        .toProvider(new AliasCommandProvider(cmd));
+    }
+  }
+
   private void configureRequestScope() {
     bind(SshScope.Context.class).toProvider(SshScope.ContextProvider.class);