Add support to check if the url has changed for a git dep and create a new clone.

gclient_scm.py

Index: gclient_scm.py
===================================================================
--- gclient_scm.py	(revision 79296)
+++ gclient_scm.py	(working copy)
@@ -186,6 +186,23 @@
       verbose = ['--verbose']
       printed_path = True
 
+    # See if the url has changed
+    current_url = self._Capture(['config', 'remote.origin.url'])
+    if current_url != url:
+      print('_____ switching %s to a new upstream' % self.relpath)
+      # Make sure it's clean
+      self._CheckClean(rev_str)
+      # Switch over to the new upstream
+      self._Run(['remote', 'set-url', 'origin', url], options)
+      quiet = []
+      if not options.verbose:
+        quiet = ['--quiet']
+      self._Run(['fetch', 'origin', '--prune'] + quiet, options)
+      self._Run(['reset', '--hard', 'origin/master'] + quiet, options)
+      files = self._Capture(['ls-files']).splitlines()
+      file_list.extend([os.path.join(self.checkout_path, f) for f in files])
+      return
+
     if revision.startswith('refs/heads/'):
       rev_type = "branch"
     elif revision.startswith('origin/'):
@@ -198,7 +215,7 @@
 
     if not os.path.exists(self.checkout_path):
       self._Clone(revision, url, options)
-      files = self._Capture(['ls-files']).split()
+      files = self._Capture(['ls-files']).splitlines()
       file_list.extend([os.path.join(self.checkout_path, f) for f in files])
       if not verbose:
         # Make the output a little prettier. It's nice to have some whitespace