Add ssh command to enable plugins

Now that we can show which plugins are disabled, it is nice to
enable them again when needed.

Change-Id: Ib4648408b1365fcd09a616f8e14f5cfbbf9a0dcb
Signed-off-by: Brad Larson <bklarson@gmail.com>

Documentation/cmd-index.txt

@@ -129,6 +129,9 @@ link:cmd-show-queue.html[gerrit show-queue]::
 link:cmd-plugin-install.html[gerrit plugin add]::
     Alias for 'gerrit plugin install'.
 
+link:cmd-plugin-enable.html[gerrit plugin enable]::
+    Enable plugins.
+
 link:cmd-plugin-install.html[gerrit plugin install]::
     Install/Add a plugin.
 

Documentation/cmd-plugin-enable.txt

@@ -0,0 +1,44 @@
+plugin enable
+=============
+
+NAME
+----
+plugin enable - Enable plugins.
+
+SYNOPSIS
+--------
+[verse]
+'ssh' -p <port> <host> 'gerrit plugin enable'
+  <NAME> ...
+
+DESCRIPTION
+-----------
+Enable plugins currently disabled. The plugins will be enabled by renaming
+the plugin jars in the site path's `plugins` directory from
+`<plugin-jar-name>.disabled` to `<plugin-jar-name>`.
+
+ACCESS
+------
+Caller must be a member of the privileged 'Administrators' group.
+
+SCRIPTING
+---------
+This command is intended to be used in scripts.
+
+OPTIONS
+-------
+<NAME>::
+	Name of the plugin that should be enabled.  Multiple names of
+	plugins that should be enabled may be specified.
+
+EXAMPLES
+--------
+Enable a plugin:
+
+====
+	ssh -p 29418 localhost gerrit plugin enable my-plugin
+====
+
+GERRIT
+------
+Part of link:index.html[Gerrit Code Review]

Documentation/dev-plugins.txt

@@ -402,6 +402,9 @@ link:config-gerrit.html#plugins.checkFrequency[plugins.checkFrequency].
 For disabling plugins the link:cmd-plugin-remove.html[plugin remove]
 command can be used.
 
+Disabled plugins can be re-enabled using the
+link:cmd-plugin-enable.html[plugin enable] command.
+
 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginLoader.java

@@ -201,6 +201,25 @@ public class PluginLoader implements LifecycleListener {
     }
   }
 
+  public void enablePlugins(Set<String> names) throws PluginInstallException {
+    synchronized (this) {
+      for (String name : names) {
+        Plugin off = disabled.get(name);
+        if (off == null) {
+          continue;
+        }
+
+        log.info(String.format("Enabling plugin %s", name));
+        File on = new File(pluginsDir, off.getName() + ".jar");
+        off.getSrcJar().renameTo(on);
+
+        disabled.remove(name);
+        runPlugin(name, on, null);
+      }
+      cleanInBackground();
+    }
+  }
+
   @Override
   public synchronized void start() {
     log.info("Loading plugins from " + pluginsDir.getAbsolutePath());

gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/DefaultCommandModule.java

@@ -49,6 +49,7 @@ public class DefaultCommandModule extends CommandModule {
 
     command(gerrit, "plugin").toProvider(new DispatchCommandProvider(plugin));
     command(plugin, "ls").to(PluginLsCommand.class);
+    command(plugin, "enable").to(PluginEnableCommand.class);
     command(plugin, "install").to(PluginInstallCommand.class);
     command(plugin, "reload").to(PluginReloadCommand.class);
     command(plugin, "remove").to(PluginRemoveCommand.class);

gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/PluginEnableCommand.java

@@ -0,0 +1,48 @@
+// 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.sshd.commands;
+
+import com.google.common.collect.Sets;
+import com.google.gerrit.common.data.GlobalCapability;
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.server.plugins.PluginInstallException;
+import com.google.gerrit.server.plugins.PluginLoader;
+import com.google.gerrit.sshd.SshCommand;
+import com.google.inject.Inject;
+
+import org.kohsuke.args4j.Argument;
+
+import java.util.List;
+
+@RequiresCapability(GlobalCapability.ADMINISTRATE_SERVER)
+final class PluginEnableCommand extends SshCommand {
+  @Argument(index = 0, metaVar = "NAME", required = true, usage = "plugin(s) to enable")
+  List<String> names;
+
+  @Inject
+  private PluginLoader loader;
+
+  @Override
+  protected void run() throws UnloggedFailure {
+    if (names != null && !names.isEmpty()) {
+      try {
+        loader.enablePlugins(Sets.newHashSet(names));
+      } catch (PluginInstallException e) {
+        e.printStackTrace(stderr);
+        throw die("plugin failed to enable");
+      }
+    }
+  }
+}