git-pw: Make git-pw work with older versions of GitPython

The search_parent_directories parameter is relatively new and older
versions of GitPython don't have it. The default was, and still is, to
recurse in parent directories so we don't actually need to specify it at
all.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>

git-pw/git-pw

@@ -188,7 +188,7 @@ class GitPatchwork(object):
 
     def setup(self):
         try:
-            self.repo = git.Repo(os.getcwd(), search_parent_directories=True)
+            self.repo = git.Repo(os.getcwd())
         except git.exc.InvalidGitRepositoryError as e:
             if self.cmd.need_git_repo:
                 die('Not a git repository.')