Use clone and push to create branches

Generalize workdir creation for git and hg and create branches in
clones instead of the scm repository, so that hooks will be fired
correctly once the changes are pushed back.

Missing:

- Evaluation of the git response from the push command
- configuration of the hg environment and the authentication, so that
  the scmhooks.py script can be triggeret correctly and can callback
  the scm manager

scm-plugins/scm-hg-plugin/src/main/java/sonia/scm/web/HgServletModule.java

@@ -46,6 +46,8 @@ import sonia.scm.plugin.Extension;
 import sonia.scm.repository.HgContext;
 import sonia.scm.repository.HgContextProvider;
 import sonia.scm.repository.HgHookManager;
+import sonia.scm.repository.spi.HgWorkdirFactory;
+import sonia.scm.repository.spi.SimpleHgWorkdirFactory;
 
 /**
  *
@@ -81,5 +83,7 @@ public class HgServletModule extends ServletModule
 
     // bind servlets
     serve(MAPPING_HOOK).with(HgHookCallbackServlet.class);
+
+    bind(HgWorkdirFactory.class).to(SimpleHgWorkdirFactory.class);
   }
 }