Fix param format of Repo.commit

Signed-off-by: Chenxiong Qi <qcxhome@gmail.com>

Author: tkdchen

git/repo/base.py

@@ -471,8 +471,10 @@ def config_writer(self, config_level="repository"):
 
     def commit(self, rev=None):
         """The Commit object for the specified revision
+
         :param rev: revision specifier, see git-rev-parse for viable options.
-        :return: ``git.Commit``"""
+        :return: ``git.Commit``
+        """
         if rev is None:
             return self.head.commit
         return self.rev_parse(str(rev) + "^0")