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Date: Tue, 12 Mar 2002 10:58:45 +0300
From: Hans Reiser <reiser@namesys.com>
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To: James Antill <james@and.org>
CC: Larry McVoy <lm@bitmover.com>, Tom Lord <lord@regexps.com>,
        jaharkes@cs.cmu.edu, linux-kernel@vger.kernel.org
Subject: Re: linux-2.5.4-pre1 - bitkeeper testing
In-Reply-To: <Pine.GSO.4.21.0203110051500.9713-100000@weyl.math.psu.edu>	<3C8C4B8A.2070508@namesys.com> <nn4rjmoh02.fsf@code.and.org>
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Clearcase handles all of this in the filesystem, and it all works pretty 
much reasonably.  Lots of details, but let's worry about them after we 
have a patch, shall we?....

Hans

James Antill wrote:

>Hans Reiser <reiser@namesys.com> writes:
>
>>Alexander Viro wrote:
>>
>>>On Mon, 11 Mar 2002, Hans Reiser wrote:
>>>
>>>>So the problem was that it was not optional?
>>>>
>>>The problem is that it doesn't play well with other things.
>>>
>>Your statement is information free so far, but could be the intro to
>>an informative statement....;-)
>>
>
> Think about what people want to do with SCM, think about how the
>filesystem can help.
> Just having a special flag to open() that enables versioning on close()
>is useless to 99% of people IMO.
>
> For something like that to be worth it it'd need to support rename(),
>symlink(), link(), unlink() and _importantly_ chmod()/chown() (you
>don't want previous versions of a file becoming readable just because
>you chmod() the final version).
>
> Off the top of my head the places where I might find a use for it...
>
>1. tar -x ... hack ... tell fs to generate diff
>   (can be done via. cp -al now, but possibly easier with fs support)
>
>2. Version control my mail box (the good readers have the mark deleted
>and then purge, which removes some of the need). Version control
>might be clumsy (say you delete 3 mails, and want only one back), and
>doesn't work with a mailer that does any caching on the mailbox.
>
>3. Putting an entire website under it.
>
>...and all but 3. are probably better done a different way (a shared
>library might be nice ... and would also be fs/kernel independent) and
>I'd imagine it's overkill for 3. as the biggest problem is saving over
>the wrong filename so undelete is enough.
>



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