add_inventory_by_delta raises errors.RootMissing()

[shuerhaaken]

A few days ago I added my project, that is using mercurial and is hosted on googlecode to launchpad.
Unfortunately the code import does not work.
The project:
https://launchpad.net/xnoise

There also the import logs can be found in the code section. They report some problem with code import:
Traceback (most recent call last):
  File "/srv/importd.launchpad.net/production/launchpad-rev-9420/scripts/code-import-worker.py", line 82, in <module>
    sys.exit(script.main())
  File "/srv/importd.launchpad.net/production/launchpad-rev-9420/scripts/code-import-worker.py", line 77, in main
    return import_worker.run()
...

[Jelmer Vernooij (jelmer)]

There are no code imports for xnoise at the moment; what's the error you're getting?

[shuerhaaken (shkn)]

Now I re-added the code import for xnoise and the errors came back:
https://code.launchpad.net/~shkn/xnoise/default

[Andi Albrecht (andialbrecht)]

This happens for me too. As with xnoise it's a Mercurial repository hosted at Google Code. The import branch is lp:crunchyfrog

[Andi Albrecht (andialbrecht)]

For me it turned out that the first commit caused the troubles. IIRC this commit was auto-generated by Google Code and contains no delta (see http://code.google.com/p/crunchyfrog/source/detail?r=43079b00fe0cdca66cdf3f5ba648f5d227cd37e6).

An import using "bzr pull" with bzr-hg plugin worked for me after making the following changes, i.e. ignoring the first revision when it's empty. I bet that this is a very bad hack since it changes commit history and that there are much better approaches :)

=== modified file 'fetch.py'
--- fetch.py 2010-10-11 11:25:55 +0000
+++ fetch.py 2010-11-15 11:40:44 +0000
@@ -375,13 +375,19 @@
     def _add_inventories(self, todo, mapping, pb):
         assert isinstance(todo, list)
         total = len(self._revisions)
+ force_null_revision = False
         # add the actual revisions
         for i, (revid, (manifest, flags)) in enumerate(self._target_overlay.get_manifest_and_flags_by_revids(todo)):
             pb.update("adding inventories", i, len(todo))
             rev = self._revisions[revid]
             files = self._files[rev.revision_id]
             del self._files[rev.revision_id]
- if rev.parent_ids == ():
+ if rev.parent_ids == () and not files and i == 0:
+ force_null_revision = True
+ continue
+ if rev.parent_ids == () or force_null_revision:
+ force_null_revision = False
+ rev.parent_ids = ()
                 basis_revid = NULL_REVISION
             else:
                 basis_revid = rev.parent_ids[0]