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Re: enforcing LF-normalization for svn:eol-style=native files (issue #4065)

From: Daniel Shahaf <d.s_at_daniel.shahaf.name>
Date: Mon, 10 Dec 2012 13:47:11 +0200

Branko Čibej wrote on Mon, Dec 10, 2012 at 11:51:08 +0100:
> On 10.12.2012 11:31, Daniel Shahaf wrote:
> > Branko Čibej wrote on Mon, Dec 10, 2012 at 00:26:20 +0100:
> >> On 10.12.2012 00:08, Johan Corveleyn wrote:
> >>> On Sun, Dec 9, 2012 at 11:43 PM, Daniel Shahaf <d.s_at_daniel.shahaf.name> wrote:
> >>>> Johan Corveleyn wrote on Sun, Dec 09, 2012 at 21:15:24 +0100:
> >>>>> 2) Am I the only one who wants to protect his repository against this
> >>>>> corruption? Judging from [1], I don't think so. It doesn't make sense
> >>>>> that everyone starts writing this pre-commit hook, for something that
> >>>>> IMHO is an obvious anti-corruption protection. I think every
> >>>>> repository out there deserves to be protected against this.
> >>>>>
> >>>> FWIW, I suggested a hook because you could implement that in about
> >>>> 5 minutes, whereas doing a C code change would take at least 10 times
> >>>> that (and several weeks if you have to wait for it to appear in a 1.7.x
> >>>> release that you can install at $WORK). I won't object to C code
> >>>> verifying the svn:eol-style invariant.
> >>> Thanks. And your pre-commit hook example is much appreciated.
> >>>
> >>> For the moment I get the impression that it's not really doable /
> >>> desirable to implement this in the repository. At least until now
> >>> no-one has suggested how it could be done, and I don't know enough
> >>> myself about the server-side / back-end to figure it out :-).
> >> The first obstacle is that the server does not interpret properties.[1]
> >> Therefore, you'd have to implement this check at transaction-commit
> >> time, because there's no earlier point where you're guaranteed to have
> >> all node properties at their final values. This implies that the time to
> >> reject a commit would be proportional to the size of the commit (which
> >> isn't the case when it comes to conflict detection).
> > Can't you do what stefan2 suggested, but in libsvn_repos? The repos
> > layer commit editor would remember for each file whether its textdelta
> > has added a new 0x0D byte, then at close_edit() it would iterate all
> > files in the commit --- and for each file only compare its svn:eol-style
> > property to the by-now-precomputed "did it it contain a 0x0D" bit.
> >
> > I'm not sure how efficient it would be to parse for 0x0D's in
> > libsvn_repos, though. Maybe we should make this optional.
> It's not enough to just look for \r in the delta stream. Certainly
> wouldn't help with historically broken files.

I wasn't trying to fix historically broken files. (That would require
a fulltext scan --- that's not a cheap computation.) Do you see another

> Maybe that's a good idea, but /why/ put it in libsvn_repos when it's
> much easier and cleaner to just provide some standard hooks, written in
> C and distributed with releases, that the admin plug in if she feels
> like it? Surely that's what hooks are for.

The argument is that a Subversion server should be enforcing
Subversion's invariants.

That said, I'm not opposed to doing it via standard hooks. It's a good
way to introduce the feature in a way that allows more easily changing
it before it hits the APIs and their strict compatibility rules.

> -- Brane
> --
> Branko Čibej
> Director of Subversion | WANdisco | www.wandisco.com
Received on 2012-12-10 12:47:50 CET

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