Fix docstring order in ghpull

hggithub/__init__.py

@@ -165,8 +165,8 @@ def ghclone(ui, git_fork_url, git_upstream_url, working_directory, **opts):
 
 @command(b"ghpull", [], _(""))
 def ghpull(ui, repo, **opts):
-    os.chdir(repo.root)
     """Prepare working directory to work with github"""
+    os.chdir(repo.root)
     git_repo = ui.config("gitrepo", "gitrepo")
     try:
         _ghpull(git_repo)