convert: allow the converter_source to say "skip this revision" If getchanges returns a string, it's assumed to be the id of an already converted revision. We map the current revision to the same revision this converted revision was mapped to. To allow skipping a root revision, getchanges can return the special string 'hg-convert-skipped-revision' (a.k.a. common.SKIPREV), which hopefully won't clash with any real id. The converter_source is responsible for rewriting the parents of the commit objects to make sure the revision graph makes sense.

adding a
marked working directory as branch b
adding b
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
fast-forward
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
bogus fast-forward should fail
abort: there is nothing to merge, just use 'hg update' or look at 'hg heads'
done