On 2009-02-26 16:36, Antoine Pitrou wrote:
> 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)).

So just to get this right: The Subversion admins on python.org do
not have to setup anything special for DVCS mirror sites to hook
up to the main Subversion repo.

>> 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.

This is probably a matter of Internet connection bandwidth then.
I have no idea how much data gets transferred, but it doesn't
"feel" slow.

>> 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.

IMHO, those are all feel-good factors which can easily be had by
installing a local Subversion repo copy (sync'ed using svnsync (*)),
except perhaps regarding merging - but I don't know anything about
in what way the DVCSes are better than Subversion.

(*) This provides fast reads. Writes will still have to to the
main repo site. See
http://subversion.tigris.org/svn_1.5_releasenotes.html#webdav-proxy

>> 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.

Right, which is what I was describing... you copy your local trunk
copy and then switch that copy to the new branch. If you use cp -al
for this, that's a very fast operation on Unixes and avoids
most of the network traffic.

Then you work in the new local branch dir.
Finally, you merge back the changes to trunk and delete the
local branch dir (and probably also the one in the repo).