If the destination directory doesn't contain the desired repo, delete it

gclient.py

Index: gclient.py
diff --git a/gclient.py b/gclient.py
index d1b5a8733859fb76b7cc28e825b941f19ad8ab01..9af52928cbaffd64a1199229b591e90ad2ffb1fc 100755
--- a/gclient.py
+++ b/gclient.py
@@ -668,6 +668,41 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
             command, options, parsed_url, self.parent.name, revision_overrides)
         self._used_scm = gclient_scm.CreateSCM(
             parsed_url, self.root.root_dir, self.name)
+
+        # When updating, determine whether the destination directory contains a
+        # checkout of the desired repository. If not, avoid conflicts by
+        # deleting the directory before running the update.
+        # TODO(borenet): Only enabling this on a few bots at first.
+        import socket
+        if (command == 'update' and
+            socket.gethostname() in ('vm859-m1', 'build1-m1', 'vm630-m1') and

[M-A Ruel, 2014/01/10 16:41:47]

Extract this in a function. I highly dislike this, you should rely on flags or
an environment variable. Add an ETA to remove this hack if you want to keep it.

[borenet, 2014/01/10 19:27:23]

Done.  When this is submitted, I will submit a try on one or all of these bots
which plays with the DEPS file.  If nothing terrible happens, I'll remove the
guard.

+            os.environ.get('CHROME_HEADLESS')):
+          logging.warning('Experimental deletion of mismatching checkouts '
+                          'enabled.')
+          actual_remote_url = self._used_scm.GetRemoteURL(options)
+          url, _ = gclient_utils.SplitUrlRevision(parsed_url)
+          url = url.rstrip('/')
+          dest_dir = os.path.join(self.root.root_dir, self.name) 
+          if os.path.isdir(dest_dir) and actual_remote_url != url:
+            should_delete = options.force or os.environ.get('CHROME_HEADLESS')
+            if sys.__stdout__.isatty() and not should_delete:

[M-A Ruel, 2014/01/10 16:41:47]

Move the check/prompt into a function.
This shouldn't prompt when --force is used.
As a matter of fact, I don't think the prompt is necessary. There is --reset for
this logic.

[borenet, 2014/01/10 19:27:23]

Done.  The prompt is not displayed with --force.  I can remove the prompt and
just fail instead?  That would be simpler and should only make a difference for
humans.  I don't know how --reset interacts with this.

[M-A Ruel, 2014/01/13 17:31:38]

Yes, I prefer failing to prompting.

Prompting the user in the middle of a sync was a Very Bad Idea (tm).

[borenet, 2014/01/13 18:17:57]

Done.

+              usr_input = ''
+              while usr_input not in ('y', 'n'):
+                usr_input = raw_input('%s does not contain a checkout of %s. '
+                                      'Do you want to delete the directory? '
+                                      'If not, the update will be canceled '
+                                      '(y/n): ' % (dest_dir, url)).lower()
+              should_delete = (usr_input == 'y')
+            if should_delete:
+              logging.warning('%s does not contain a checkout of %s. Removing '
+                              ' %s' % (dest_dir, url, dest_dir))
+              gclient_utils.rmtree(dest_dir)
+            else:
+              raise gclient_utils.Error('%s does not contain a checkout of %s. '
+                                        'Please fix the solution manually or '
+                                        'run with --force to delete '
+                                        'automatically.' % (dest_dir, url))
+
         self._got_revision = self._used_scm.RunCommand(command, options, args,
                                                        file_list)
         if file_list: