Re: [RFC PATCH 0/3] Towards a Git-to-SVN bridge

[Ramkumar Ramachandra <artagnon@gmail.com>]

Hi Jonathan,

Jonathan Nieder writes:
> Ramkumar Ramachandra wrote:
> 
> > Over the last couple of days, I've been working on a parser that
> > converts a fast-import stream into a SVN dumpfile. So far, it's very
> > rough and works minimally for some common fast-import
> > commands.
> 
> Some early questions:

Thanks for raising these questions. People interested in the project
should find this useful.

>  - what are the design goals?  Is this meant to be super fast?
>    Robust?  Simple?  Why should I be excited about it?[1]

I want it to be a lot like current svn-fe: as you can see, I've
re-used many parsing ideas from it. It has to be atleast as fast as
svnrdump, because I don't want it to bottleneck in the remote helper
pipeline. It has to be simple because it'll give rise to other simple
remote helpers- all the complexity has to be offloaded onto the lower
layers like fast-import/ fast-export, and not onto the developer of
the remote helper.

>  - what subset of fast-import commands is supported?  Is it well
>    enough defined to make a manpage?

Currently, it supports just "commit", "blob", "author", "committer"
and "mark" that appear after a blob. It should support more commands
soon enough- this implementation is just a proof of concept. Also,
Instead of giving it the ability to parse /any/ valid fast-import
stream, I want to simply focus on parsing the stream produced by git
fast-export. That should explain why I'm trying to patch git
fast-export primarily.

>  - does this produce v2 or v3 dumpfiles?

This is one issue I haven't thought about fully yet. I'm currently
thinking of generating a non-deltified dumpfile v3 -- something that
svnrdump will accept. Generating deltas might be an unnecessary
overhead- but as you pointed out yesterday, that clearly needs more
thought.

>  - why would I use this instead of git2svn?  Does git2svn do anything
>    this will not eventually be able to do?  (Not a trick question ---
>    I don't have enough experience with git2svn to tell its strengths
>    and weaknesses.)

git2svn persists blobs in-memory. It's written in Perl and it's
slow. I thought we needed something nicer to be used with a remote
helper, and started writing svn-fi.

> > I've decided to try re-implementing fast-export
> > to eliminate blob marks
> 
> Hopefully "re-implement" means "patch" here. :)

Yep. Just a big one :)

> I can comment on the code but it's probably better if I have a sense
> of the design first (in any event, thanks for sending it).

I haven't had time to clean up the code. Note that it "just works" at
the moment- yes, it's already very very fast :) However, I'm going to
stall the branch and work on fast-export-inline for now.

-- Ram