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Re: Q: identical files "shared" in repository?

From: John Peacock <jpeacock_at_rowman.com>
Date: 2005-04-11 13:01:51 CEST

Ph. Marek wrote:
> I believe I can't make myself really clear. Sorry, I'll try again:
> If there are many files with identical data, are they stored in the repository
> multiple times or are they referenced to a common block?

The latter. When making a copy (branch or tag are equivalent here) of a file,
the repository simply notes that this new copy points to the old file contents
(and indeed where that is located is also saved as a special copy-from
attribute). When you change that file, the contents are then physically copied
from the original file and your modifications applied (I think this part is
accurate). So branches are as close to zero "cost" as possible (effectively
headers only until you make a change to any file).

When you are using a command that understands history, the copy-from attribute
allows you to walk back past the point where the file was copied (for example,
using `svn annotate`). At some point (probably not until 2.0), there will be a
matching copy-to attribute, so you could apply a bugfix to a file and all of
it's decendants too (if you had multiple client specific branches, for example).



John Peacock
Director of Information Research and Technology
Rowman & Littlefield Publishing Group
4720 Boston Way
Lanham, MD 20706
301-459-3366 x.5010
fax 301-429-5747
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Received on Mon Apr 11 12:58:55 2005

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