Handle '@' symbol in ssh username

http://youtrack.jetbrains.com/issue/IDEA-123890
Git pull doesn't work if git username has 'at' symbol

plugins/git4idea/rt/src/org/jetbrains/git4idea/ssh/SSHMain.java

@@ -471,7 +471,7 @@ public class SSHMain implements GitExternalApp {
     }
     String host = args[i++];
     String user;
-    int atIndex = host.indexOf('@');
+    int atIndex = host.lastIndexOf('@');
     if (atIndex == -1) {
       user = null;
     }