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 c3e295c42e1dca0fff893a61352cfa7deee4fe36..e17238d11b6c278e0c750ba8dd99a522ee4a5d8b 100755
--- a/gclient.py
+++ b/gclient.py
@@ -641,6 +641,36 @@ 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.
+        if command == 'update':
+          actual_remote_url = self._used_scm.GetRemoteURL(options)
+          url, _ = gclient_utils.SplitUrlRevision(parsed_url)
+          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
+            if not should_delete:
+              if sys.__stdout__.isatty():
+                usr_input = None
+                print ('%s does not contain a checkout of %s. Do you want to '
+                       'delete it before attempting to update?' % (dest_dir,
+                                                                   url))
+                while usr_input not in ('y', 'n'):
+                  print 'Please type "y" or "n".'
+                  usr_input = raw_input()

[iannucci, 2013/11/14 07:38:15]

raw_input() takes a prompt, which would be a bit better than the print, I think.

[borenet, 2013/11/14 18:31:21]

Done.

+                should_delete = (usr_input == 'y')
+              else:
+                logging.warning('%s does not contain a checkout of %s. Not '
+                                'attempting to remove automatically. Re-run '
+                                'with "--force" to automatically remove '
+                                'conflicting checkouts.' % (dest_dir, url))
+            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)
+

[borenet, 2013/11/13 19:12:24]

I'd like to point out that this causes some strange (to me) behavior when we
don't delete the destination directory: if no files conflict, you end up with
*both* checkouts.  In my test I tried to add verification that the syncs failed
without --force and then succeeded with --force.  However, since I'm checking
out two different repos (one in git, the other in svn), nothing conflicted and I
ended up with both checkouts in the same directory.  I think in practice this
won't be an issue, but it's worth thinking about.

[iannucci, 2013/11/14 07:38:15]

I'm inclined to just abort if we didn't end up deleting by this point. If it's a
dev, then they need to take care of it manually (or press 'y'), and if it's a
bot, it's running with '--force'.

[borenet, 2013/11/14 18:31:21]

Sounds fine to me, but I think it might also be okay for the user to take
responsibility for what happens if they don't take the recommended action.

[iannucci, 2013/11/14 18:45:25]

Yeah, I agree, the thing is that the gclient solution will be in a totally weird
state, and it won't be clear what to do about it. Moreover, it will appear as if
gclient 'worked', and so the user may not even know that they're in a weird
state for along time afterwards. If we abort, then the user will be manually
forced to move the repo aside, delete it, or re-run gclient and press 'y'
instead of 'n'.

[borenet, 2013/11/15 13:46:48]

SGTM.  Changed to raise Error if the directory isn't deleted.

         self._got_revision = self._used_scm.RunCommand(command, options, args,
                                                        file_list)
         if file_list: