Reusable fastimport parser

[Greg Ward]

Hi all --

no doubt you folks are aware that there is well designed, high
performance, low overhead, pure Python parser for git's "fastimport"
format in bzr-fastimport.  The original author of hg-fastimport
clearly liked it enough that now we have two copies of Ian
Clatworthy's fastimport parser kicking around the net: hg-fastimport
is basically a fork of bzr-fastimport with the backend rewritten to
produce a Mercurial repository.

Well, I'm now the maintainer of hg-fastimport, since I committed the
fatal error of sending patches to the original author after he lost
interest.  D'ohhh.  And I really don't like fixing bugs that other
people have already fixed, nor do I like it when my fixes do not
benefit the widest possible audience.

So... I'd like to heal the fork before it gets bad.  IMHO the best
option would be factor out the non-Bazaar-specific bits of
bzr-fastimport and put them in a common library that both
bzr-fastimport and hg-fastimport depend on.  Does that sound
agreeable?  Any better ideas?

If that sounds good, what about Dulwich?  That's an implementation of
of Git's protocols and file formats in pure Python; seems like a good
place for a common, reusable fastimport parser to live.  I haven't
asked the Dulwich maintainers what they think of this idea, but
whatever.  Thought I'd start here.  Feedback?

Thanks --

Greg