Vadim Zeitlin <vz-git@zeitlins.org> wrote:
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> Hello, > > First of all, let me use this opportunity to thank you for writing > git-svn, it's the best thing since, well, probably git itself! Second, > I'm sorry to bother you directly but I simply couldn't find any mailing > list for git-svn and I wasn't sure if this was appropriate for the git > mailing list itself. If I was wrong about not posting this there, please > feel free to redirect/reply to git list if you prefer to discuss it there > (I'd appreciate if you could still cc me in this case though).
Hello Vadim, you're welcome!
git-svn has always used the git mailing list. Feel free to Cc maintainers of particular subsections even when posting to the mailing list, too. The mailing list gets a lot of traffic, so we always Cc folks who are relevant to the discussion.
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> Now to my question: I thought it would be a good idea to import an svn > repository with --no-metadata option as I hoped that this would avoid the > rewriting of commits which happen when git topic branches are checked in > into svn with "git svn dcommit". The documentation (for my 1.7.1 version) > did say that:
dcommit would have to rewrite commits anyways, since we sync the usernames and commit times from SVN. You can't avoid rewriting commits unless you use "git svn set-tree" (on the other hand, set-tree can be unfriendly to other SVN users).
> If you lose your .git/svn/git-svn/.rev_db file, git svn will not be > able to rebuild it and you won't be able to fetch again, either.
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> but I understood it as meaning that I wouldn't be able to fetch again if
> the file was lost (the file name appears to be wrong BTW, since the switch
> to rev_map from rev_db some time ago) and thought that it was ok as long as
> I took care to backup the .git/svn contents regularly. Apparently I was
> wrong as "git svn fetch" doesn't work even immediately after the import and
> looking at the code I see that working_head_info() only ever uses
> git-svn-id: lines in the commit messages and never rev_{db,map} files.
>
> So -- finally -- the questions are:
>
> 1. Is this indeed the case, i.e. is importing from svn really impossible
> with --no-metadata even if no files are lost? If so, I think it would
> be nice to make the property description in the man page more clear.rev_map (and rev_db before it) are designed for mapping SVN revision numbers into git SHA1 identifiers. rev_db used a simple but space-inefficient offset lookup based on the SVN revision number. rev_map uses a binary search also based on the SVN revision number.
> 2. Is it possible to implement getting the working head info from the > cached revision mappings instead of extracting it from the comments? > If so, would it be worth looking into doing this or is it something > that is doomed to fail anyhow?
It's possible to do a reverse mapping inefficiently (O(n)) by scanning the values of the SHA1 commits. You can add a hash database on disk, too. I don't think either is worth the effort in maintenance, though. Nowadays git-filter-branch is in mainline git, and I recommend using that for projects ready to drop SVN/git-svn entirely for git.
I'll update the docs accordingly.
-- Eric Wong
