Update JGit to 2.2.0.201212191850-r

Upstream JGit released this on Thu Dec 20 2012.

Change-Id: I91cd819c906b268284a553e1738e7fb62399da05
diff --git a/pom.xml b/pom.xml
index 58c6278..615e3c3 100644
--- a/pom.xml
+++ b/pom.xml
@@ -46,7 +46,7 @@
   </issueManagement>
 
   <properties>
-    <jgitVersion>2.1.0.201209190230-r</jgitVersion>
+    <jgitVersion>2.2.0.201212191850-r</jgitVersion>
     <gwtormVersion>1.5</gwtormVersion>
     <gwtjsonrpcVersion>1.3</gwtjsonrpcVersion>
     <gwtexpuiVersion>1.2.7</gwtexpuiVersion>