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Re: Supporting the "Labels" feature of CVS in SVN.

From: Steven Bakke <steven.bakke_at_amd.com>
Date: 2007-08-10 14:57:48 CEST

On Aug 9, 2007, at 12:53 PM, Les Mikesell wrote:

> Shawn Talbert wrote:
>> Rather than copies (tagging), could one not use a custom property
>> to do this
>> [having a "label" attached to multiple versions of the same file]?
>
> Usually the point of the tag is to be able to find the revision you
> want without checking anything else and with svn's 'cheap copy'
> method it is a reasonable approach. The only real down side
> compared to CVS is that you can't start from a tagged copy and look
> 'forward' to see what other revisions have been done since this
> revision was tagged.
>

There are lots of downsides to the SVN method of doing this that I
believe CVS did better.

1. There is no easy way to determine which versions of a file on your
trunk or branch are part of any given tag. Yes, you can mine the
revision logs in the entire repository to look for copies, but that
isn't what I would call easy.
2. A property would be great except that you want to apply a property
to a specific revision. You can't do this to my knowledge so it
isn't an option.
3. There isn't an efficient query mechanism for getting property
info. I would want to be able to do some arbitrary query to give me
a bunch of stuff that has an arbitrary set of properties set. This
isn't really possible.

The best that can be done at this point is to try to make subversion
tagging look like labels. However, it is not a replacement for
labels. I think it would be a very useful feature to add to
subversion say in the 2.0 timeframe. Sometimes you want a cheap
copy, but sometimes you really want a label ala CVS or Perforce.

If properties had a robust query mechanism, and you could apply
properties on arbitrary revisions, then you could change the current
'svn cp' command to apply a property to each of the source revisions
that it copied. This would enable #1 which is really the big thing
that people like about labels.

-Steve

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Received on Fri Aug 10 14:56:36 2007

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