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[python-committers] Survey about DVCSs compared to svn

Antoine Pitrou solipsis at pitrou.net
Thu Feb 26 16:36:41 CET 2009 
Le jeudi 26 février 2009 à 16:10 +0100, M.-A. Lemburg a écrit :
> 
> I didn't know that and was under the impression that those other
> systems simply hook up to the svn repo via the standard Subversion
> interfaces.

They hook up to the svn repo for mirroring purposes, true. But they also
have their own wire protocol, and some of them also have Web-based
browsing facilities (which, in the case of Mercurial, are actually two
sides of the same coin: the same base URL is used for human-readable
browsing and for read-only HTTP-based cloning of the repository (the
writeable cloning variant, as with SVN, uses an SSH-based protocol
instead)).

> However, it is often said that branches in DVCS system are so much
> better to work with. Subversion supports these as well, it's just
> that we currently don't make much use of them and that's what I
> wanted to point out.

Perhaps because they are not really practical? For example, I don't know
how often you use svnmerge, but it's surprisingly slow even for small
merges. It also seems to transfer lots of information over the network.

> I don't understand that comment. Of course, you can commit whatever
> changes you make to the branch.

Ok, sorry, I misunderstood your comment.

> By contrast, the reasons for switching from CVS to Subversion were
> mostly technical ones - we often had problems with locks and tagging
> was very slow.

There are also technical reasons to prefer a DVCS: fast logging, fast
annotation, fast (and supposedly smarter, although I'm not really
knowledgeable on this) merges, and in some cases a nifty Web front-end.

> Why is that ? You need to do that for patches that change the build
> system or configuration, but for patches to a single C file, that's
> normally not needed.

Ok, but the point is that if many files have changed (or a single file
in the Include directory :-)), the rebuild process is longish each time
you "svn switch". Not so if you use a separate directory for each line
of work.
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