gclient: Add better error reporting when path is not a git repo.

gclient_scm.py

 # Copyright (c) 2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Gclient-specific SCM-specific operations."""
 
 import logging
 import os
 import posixpath
 import re
@@ skipping 169 matching lines @@
 
     if not os.path.exists(self.checkout_path):
       self._Run(['clone', url, self.checkout_path],
                 cwd=self._root_dir, redirect_stdout=False)
       if revision:
         self._Run(['reset', '--hard', revision], redirect_stdout=False)
       files = self._Run(['ls-files']).split()
       file_list.extend([os.path.join(self.checkout_path, f) for f in files])
       return
 
+    if not os.path.exists(os.path.join(self.checkout_path, '.git')):
+      raise gclient_utils.Error('\n____ %s%s\n'
+                                '\tPath is not a git repo. No .git dir.\n'
+                                '\tTo resolve:\n'
+                                '\t\trm -rf %s\n'
+                                '\tAnd run gclient sync again\n'
+                                % (self.relpath, rev_str, self.relpath))
+
     new_base = 'origin'
     if revision:
       new_base = revision
     cur_branch = self._GetCurrentBranch()
 
     # Check if we are in a rebase conflict
     if cur_branch is None:
       raise gclient_utils.Error('\n____ %s%s\n'
                                 '\tAlready in a conflict, i.e. (no branch).\n'
                                 '\tFix the conflict and run gclient again.\n'
@@ skipping 339 matching lines @@
       print("\n________ couldn't run \'%s\' in \'%s\':\nThe directory "
             "does not exist."
             % (' '.join(command), path))
       # There's no file list to retrieve.
     else:
       self.RunAndGetFileList(options, command, path, file_list)
 
   def FullUrlForRelativeUrl(self, url):
     # Find the forth '/' and strip from there. A bit hackish.
     return '/'.join(self.url.split('/')[:4]) + url