Re: [SoC RFC] libsvn-fs-git: A git backend for the subversion filesystem

From: Jakub Narebski <jnareb@gmail.com>
Date: Mar 20, 2008, 10:01 UTC
Message-ID: <frtcmc$l8m$1@ger.gmane.org>
In-Reply-To: <20080320045632.GB8410@spearce.org>

[Cc: Shawn O. Pearce <spearce@spearce.org>, 
     Bryan Donlan <bdonlan@gmail.com>,
     git@vger.kernel.org]

Shawn O. Pearce wrote:

> Bryan Donlan <bdonlan@gmail.com> wrote:

Show 20 quoted lines

>> /revmap/NNN - a reference to the commit hash in the .git-svn branch
>>   corresponding to the given subversion revision number
> 
> How about using a simple flat file interface?  To initially prime
> the file you can do something like:
> 
>         git rev-list --topo-order --date-order --reverse --all \
>                >.git/svn-map 
> 
> and then number the revisions by the line number that they appear on.
> Locating a Git SHA-1 for a specific SVN revision would be a simple
> case of lseek(fd, 41 * rev, SEEK_SET).  Going the other direction
> would be more of a challenge, but is still doable.
> 
> Updating the file should just require appending new commits; if
> the SVN client wants a new commit you append on and return the
> line number.  If Git has caused new commits not in this file you
> need to rebuild the log.  This would have to be done incrementally,
> to prevent changing a prior SVN revision number that clients may
> already know about.

By the way, have you looked into what git-svn uses? IIRC it had some improvements to avoid spending more disk space on SVN revno <-> Git SHA-1 mapping than on the repository itself...

-- 
Jakub Narebski
Warsaw, Poland
ShadeHawk on #git