Re: [boost] Live read-only GIT mirrors of Boost trunk SVN

Subject: Re: [boost] Live read-only GIT mirrors of Boost trunk SVN
From: Dave Abrahams (dave_at_[hidden])
Date: 2013-05-07 02:44:35

on Mon May 06 2013, Niall Douglas <ndouglas-AT-blackberry.com> wrote:

> My experience with SubGit has been very, very good. I would *strongly*
> recommend it over git2svn. 

Why, have you got a lot of experience with both tools?  You'd recommend
SubGit for what job, exactly?  Does it modularize? (answer: no).

We didn't choose svn2git at random: we started using it because KDE (a
much bigger project than Boost) used it to solve the exact same problems
Boost has to solve: modularization + Git migration.

You'd have to have some pretty compelling arguments, a complete plan for
migration and modularization, and be prepared to lead the effort
yourself for me to throw out years of planning and coding to use a
different tool.  Do you really think you're making a reasonable
suggestion?

> The company which develops it has been very impressive in response
> rate and going the extra mile to help me figure out problems.
>
> BTW Dave with much help from the same company I've figured out the opposite
> flow: automated Git => Boost SVN. It took a lot of trial and error to work
> around Boost's MIME type and EOL conventions, but you can see an exact
> automated mirror of https://github.com/ned14/TripleGit at
> http://svn.boost.org/svn/boost/sandbox/triplegit/. I had to squash history
> because of the MIME type problems though :( but from now on it should be
> live.

Two way Git <-> SVN mirroring by itself is nice, but doesn't do much to
get us closer to the long-term goal of modularization.  It does seem
like a very nice way to get Boosters comfortable with Git while we
figure out modularization, but there isn't much time left...  If you
will administer the mirror, I think it it could still be useful for some
Boosters.

> I think it would be quite easy to set up a live perfect Git mirror of all
> Boost SVN, 

"Perfect," really?  I think you are grossly underestimating some of the
strange ways that the SVN filesystem has been used over Boost's history.
>From http://subgit.com/book/index.html#branches-mapping it's clear that
the SubGit tool isn't equipped to deal with them properly.  For example,
there's no revision range limiting in the branch mapping, a feature of
svn2git that we actually *need* to use.

> do a transition period where SVN is writeable but GIT read only, and
> then one day the switch is flipped and it goes the other way
> round. That way anyone dependent on SVN keeps on working, but without
> write access.

Again, I think a two-way mirror could be a really nice addition to the
existing transition plan, if someone is willing to put in the elbow
grease to set it up.  Are you volunteering?

-- 
Dave Abrahams