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Re: Older versions through http-repository browsing

From: Ben Collins-Sussman <sussman_at_collab.net>
Date: 2005-03-04 15:22:04 CET

On Mar 4, 2005, at 7:36 AM, Matthias Wächter wrote:
>
> What unit in the chain
>
> User
> ->Browser
> ->apache
> ->mod_dav
> ->mod_dav_svn
> ->database
>
> does not allow a "simple" revision number selection, for example by
> appending ?r=<rel>" to the URL?
>

There's nothing that prevents doing that. In fact,

>
>
> http://server/repos/trunk/file?r=105

... a syntax similar to this already exists, and always has. But it's
a secret.

The point is that the WebDAV/DeltaV specification forbids the syntax
from being public. DeltaV clients are supposed to send a series of
PROPFIND requests that result in the "discovery" of the URL. And once
the client has the URL, it treats it as an opaque object; it's not
allowed to understand the syntax, and it's *definitely* not allowed to
assume that the syntax will stay the same. The server might have N
different syntaxes, or might change its syntax at any time.

So: mod_dav_svn keeps the syntax private. An ordinary web browser
doesn't speak DeltaV, and therefore cannot "discover" the syntax.

Meanwhile, there are plenty of CGI programs out there explicitly made
for browsing a repository, such as ViewCVS or WebSVN. Their syntaxes
are public.

> Or is it just for the purpose of making Apps like ViewCVS or WebSVN
> sell
> at all? ;-)
>

"Sell"? Yeah, those authors are raking in the money. :-)

The fact that the syntax is private implementation detail of DeltaV is
just part of the larger picture: we don't want mod_dav_svn to develop
feature-creep and slowly morph into a big repository-browsing
application. That's why its displays of directories are so minimal;
that's why it doesn't show properties, or log messages, or anything
else. It's a DeltaV server, and nothing more. If you know DeltaV, you
can "discover" all the information you want. If you don't know DeltaV,
then talk to a good CGI browsing app.

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Received on Fri Mar 4 15:23:32 2005

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