(refs #1484)Add --plugin_dir option

src/main/java/JettyLauncher.java

@@ -48,6 +48,9 @@ public class JettyLauncher {
                         case "--temp_dir":
                             tmpDirPath = dim[1];
                             break;
+                        case "--plugin_dir":
+                            System.setProperty("gitbucket.pluginDir", dim[1]);
+                            break;
                     }
                 }
             }

src/main/scala/gitbucket/core/util/Directory.scala

@@ -32,7 +32,7 @@ object Directory {
 
   val DatabaseHome = s"${GitBucketHome}/data"
 
-  val PluginHome = s"${GitBucketHome}/plugins"
+  val PluginHome = Option(System.getProperty("gitbucket.pluginDir")).getOrElse(s"${GitBucketHome}/plugins")
 
   val TemporaryHome = s"${GitBucketHome}/tmp"