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From "Bert Huijben" <b...@qqmail.nl>
Subject RE: Checksum in --xml for svn info <repo_file>
Date Wed, 14 May 2014 12:49:06 GMT


> -----Original Message-----
> From: Dan Ellis [mailto:danellis10@gmail.com]
> Sent: dinsdag 13 mei 2014 20:13
> To: Ben Reser
> Cc: Subversion Users
> Subject: Re: Checksum in --xml for svn info <repo_file>
> 
> On Tue, May 13, 2014 at 10:16 AM, Ben Reser <ben@reser.org> wrote:
> > On 5/12/14, 2:49 PM, Dan Ellis wrote:
> >> When performing an svn info on a local working copy, I can see the file's
> >> checksum (sha-1 specifically), but this doesn't work on repositories.  It
> would
> >> be really nice and save some bandwidth if I could simply compare
> checksums
> >> versus performing a diff.  Is there support in the SVN server API that
> supports
> >> this property?  If so, is there any interest from the developers to add this
> >> xml tag?
> >
> 
> > Given that 1.8 solves your --summarize issue, unless there's some other
> use
> > case for this I'm not sure it's worth exposing.
> 
> My only use case would be one of performance.  How does the current
> implementation of a diff from a local WC file to a server repository
> file work?  Since it doesn't sound like the server can expose the
> checksum right now, I assume the client must bring over a copy of the
> file's content to do a diff against (even a summary only diff).
> Simply using a checksum comparison would be much more efficient for
> comparing large numbers of files (or files with large content).

Luckily Subversion can use much smarter tricks than this system you describe here.

Svn reports which URL at which revision you have locally (and if a directory the exceptions
on that below) to the repository, and then the repository reports back if there are any changes
if you would compare the actual trees.

In case of a normal diff the binary diff and property changes would be send to the client,
so it could reconstruct the whole file using the BASE information in the pristine store. But
as you pass --summarize the server just sends the information: 'there are changes'.

	Bert


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