Post-nonexistent-revision crash sidestepped

Fix for the bug that leaves a fractional .git directory after attempting to
perform an initial sync to a nonexistent revision. Moved the initialization of
the working directory to after the revision ID has already been checked. Now,
no project/.git directory gets created at all if the revision ID is bad.

Change-Id: I0c9b2a59573410f1d11de7661591bf02e4ce326b

project.py

@@ -691,11 +691,11 @@ class Project(object):
     """Perform only the local IO portion of the sync process.
        Network access is not required.
     """
-    self._InitWorkTree()
     all = self.bare_ref.all
     self.CleanPublishedCache(all)
-
     revid = self.GetRevisionId(all)
+
+    self._InitWorkTree()
     head = self.work_git.GetHead()
     if head.startswith(R_HEADS):
       branch = head[len(R_HEADS):]