add getVersion and listPlugin commands and update replicate command

The replication command string changed after replication became a plugin in gerrit.
This patch adds a getVersion[1] and a listPlugins[2] command to gerritlib.  The listPlugin
command is used to determine the correct replication string to execute in the replication
command.

[1] Only available on gerrit version >= 2.6
[2] Only available on gerrit version >= 2.5
Closes-Bug: #1273891
Partial-Bug: #1082781

Change-Id: I966037851b3f27536f415230edd1ae4e710321fb

gerritlib/gerrit.py

@@ -165,6 +165,7 @@ class Gerrit(object):
         self.keyfile = keyfile
         self.watcher_thread = None
         self.event_queue = None
+        self.installed_plugins = None
 
     def startWatching(self, connection_attempts=-1, retry_delay=5):
         self.event_queue = Queue.Queue()
@@ -209,8 +210,32 @@ class Gerrit(object):
         out, err = self._ssh(cmd)
         return filter(None, out.split('\n'))
 
+    def listPlugins(self):
+        plugins = self.getPlugins()
+        plugin_names = plugins.keys()
+        return plugin_names
+
+    # get installed plugins info returned is (name, version, status, file)
+    def getPlugins(self):
+        # command only available on gerrit verion >= 2.5
+        cmd = 'gerrit plugin ls --format json'
+        out, err = self._ssh(cmd)
+        return json.loads(out)
+
+    def getVersion(self):
+        # command only available on gerrit verion >= 2.6
+        cmd = 'gerrit version'
+        out, err = self._ssh(cmd)
+        out = out.split(' ')[2]
+        return out.strip('\n')
+
     def replicate(self, project='--all'):
-        cmd = 'gerrit replicate %s' % project
+        cmd = 'replication start %s' % project
+        if self.installed_plugins is None:
+            try:
+                self.installed_plugins = self.listPlugins()
+            except Exception:
+                cmd = 'gerrit replicate %s' % project
         out, err = self._ssh(cmd)
         return out.split('\n')