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AW: Re: Simple Label=RevisionID Discussion

From: Felix Gilcher <gilcher_at_exozet.com>
Date: 2006-11-22 17:22:45 CET

John Rouillard <mailto:rouilj@renesys.com> schrieb am Mittwoch, 22. November 2006 16:53:

> On Wed, Nov 22, 2006 at 09:49:01AM +0100, Robert Graf-Waczenski wrote:
>>> 2. How many labels can be attached to a revision? One? Any number?
>>
>> Only one. (Remember, we're talking *poor* man's labels here...)
>
> So adding a new label to the rev destroys the old label? I think this
> is wrong. Any given revision should be able to have the same label.
> Especially with mutable labels you may need to double label a revision
> with a permanent label (say PRODUCTION_2006_11_22) and a floating
> lable (CURRENT_PRODUCTION).

I see you're trying to replace tags by labels. You really should be aware that if a label is a revision alias it does not carry enough information to identify a production release. Regard subversion as a versioned filesystem. Every resource can be identified by 2 coordinates: a paths and a time coordinate. Time is what you specify with the revision argument to the svn command unless HEAD is implied. So what does a label "PRODUCTION" mean if it references revision X? Is it

componentY/stable/version1/ at revision X

or maybe

componentY/development/currently_broken/ at revision X

Things get even worse when you have a repository as the apache foundation [1] has: all ASF projects from ANT to xmlgraphics are in a single repository - this is quite a common usecase. What does the label "PRODUCTION" mean in this context?

So you'd have to specify

svn co -r"APR_PRODUCTION" http://svn.apache.org/repos/asf/apr/apr/trunk/

or something similar instead of

svn co http://svn.apache.org/repos/asf/apr/apr/tags/1.2.7/

Which one of the two is more error prone? Without a doubt the first one. What happens if you confuse which labels belong to which path of your project? You may get build errors or even worse build and release old, buggy versions. The current tagging mechanism is way more suited to identifying frozen revisions such as "PRODUCTION".

So what I'm missing in this discussion is what exact benefits do you all expect from labels as revision ids? What about this:

Make it possible to specify a svn url in the -r argument. If the argument is an url, it gets replaced by the revision in which the branch/tag was created. There are some corner cases (what happens if the url does not point to branch etc.), but it would be possible to create such an implementation as a shellwrapper to svn for testing purposes.

regards

felix

[1] http://svn.apache.org/repos/asf/

-- 
Felix Gilcher
Head of IT Development
Exozet Berlin GmbH
Rotherstraße 20
10245 Berlin
eMail: gilcher@exozet.com
URL: www.exozet.com
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Received on Wed Nov 22 17:24:47 2006

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