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Re: Forcing complete binary file comparison for checkin

From: Lasse Vågsæther Karlsen <lasse_at_vkarlsen.no>
Date: Mon, 4 Feb 2008 10:34:56 +0100

Not really commenting on how subversion would or should handle this but IMO
it's a really badly designed program that modifies a file but hides all
details about the modification.

Using the date/time stamp is a very typical way to see if a file has been
modified after a certain point in time.

I understand this is outside the realm of this mailing list but I would
strongly suggest modifying the program or reporting that case as a bug. For
instance, none of the image cataloging programs I use would detect that type
of change either, unless the modification was done while the program was
actively holding a change-notification handle on the folder.

So while it might be common to just change the file in place, I would
certainly not agree that it should be common that it makes sure to reset the
last changed timestamps on the file, something it has to explicitly do
because the file system automatically maintains this timestamp for you.

On Feb 3, 2008 11:33 PM, Karl Fogel <kfogel_at_red-bean.com> wrote:

> Blair Zajac <blair_at_orcaware.com> writes:
> > Andy Levy wrote:
> >> On Feb 3, 2008 1:49 AM, Sang Go <sanghgo_at_gmail.com> wrote:
> >>> SVN does not seem to detect changes in binary files that have changed,
> but
> >>> the file date, time, nor size has changed. This occurs when doing
> lossless
> >>> rotation of JPEG images where the file date and time are forced to
> retain
> >>> the original date and time.
> >>
> >> That's correct. SVN uses the date/time of the file as the primary
> >> indication that the file has changed.
> >
> > I'm pretty sure that svn 1.5 will also check the file size.
>
> Note that in this case, the sizes are also the same -- apparently, the
> program in question just does stuff to regions inside the file,
> without changing the file's size. (I think that's a common technique
> for dealing with really big files: you just do seeks-and-writes for as
> long as you can, and only after space usage gets really inefficient do
> you do an expensive resizing.)
>
> -Karl
>
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-- 
Lasse Vågsæther Karlsen
mailto:lasse_at_vkarlsen.no
http://presentationmode.blogspot.com/
PGP KeyID: 0xBCDEA2E3
Received on 2008-02-04 10:35:23 CET

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