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Re: Adding changeset-like functionality to subversion

From: Brad Appleton <brad_at_bradapp.net>
Date: 2002-10-08 21:47:07 CEST

On Tue, Oct 08, 2002 at 02:24:39PM -0500, Ben Collins-Sussman wrote:
> Subversion has changesets, but they're sort of implicit. Each
> subversion commit *does* have a unique name -- the revision number.

What is it the revision number of if it is not specific to
one and only one file? Is it a repository version? Do I get to
choose the "ID" or is it assigned for me? (if it is the latter,
do I get to create a more mnemonic and symbolic name for it too?)

> If I understand correctly, a pure changeset system stores
> the *changesets* (i.e. patches) as first-class objects,
> and the trees are derived artifacts that come from mixing
> and matching them.

It depends on the tool implementation. If you mean the
"pure" implementation based on the original definition put
forth by Aide De Campe (now TrueChange) then I belive you are
correct. It is JUST the deltas, as there is a unique id for each
change-set across all file archives in the repository. There
is a semi-famous paper by Darcy Wiborg Weber of Continuus (CM
Synergy) fame entitled something like "Change-Sets versus
Change-Packages" that talks about the exact details you mention,
and that they can both achieve equivalent functionality but
with different tradeoffs.

> think this is how Bitkeeper works, no?

I don't know the specifics of the BitKeeper implementation. (And
judging by Brian's previous posting I couldn't discuss it even if
I did :-). What I do know is from the BitKeeper docs on their
website (and from a write-up I did in the upcoming "SCM Patterns"
book) for which I got Larry McVoy's personal blessing on what
was written about BitKeeper :-). A BitKeeper change-set
captures enough information so that BitKeeper knows not just
the set of file changes/revisions, but it also knws what was
the state of the rest of the workspace/repository when it was
"committed"

-- 
Brad Appleton <brad_at_bradapp.net>  http://www.bradapp.net/
 "Education is the ability to listen to almost anything
  without losing your temper or your self-confidence."
   -- Robert Frost
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Received on Tue Oct 8 21:48:08 2002

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