Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!mdisea!mitchell
From: mitchell@MDI.COM (Bill Mitchell)
Newsgroups: comp.os.minix
Subject: Re: Trouble with AM - a solution ?
Message-ID: <1991May27.005131.24523@MDI.COM>
Date: 27 May 91 00:51:31 GMT
References: <1991May25.144403.318@MDI.COM> <29875@hydra.gatech.EDU>
Organization: Motorola, Mobile Data Division - Seattle, WA
Lines: 48

In article <29875@hydra.gatech.EDU> gt0178a@prism.gatech.EDU (Jim Burns) writes:
>in article <1991May25.144403.318@MDI.COM>, mitchell@MDI.COM (Bill Mitchell) says:
>
>> 1.  CRC of the file to be patched.
>>     Don't patch it unless the CRCs match
>>     User must have an exact copy of the file-to-be-patched.
>
>This will cause havoc trying to keep straight 'official patches' from net
>supplied patches. Net patches can be supplied relative to some well known,
>official patch, but then all net patches after that will fail on the CRC.
>Won't be too bad if the number of CRC checking patches are kept to a
>minimum; otherwise there will be a lot of hand editing. Of course, since
>this is being proposed as a solution to massive re-writes including gobs
>of copyright code in the cdiff, all future patches would be difficult to
>apply anyway, so this would be the obvious case that CRC checking patches
>would be limited to.
>-- 

I thought I had followed this up, but haven't seen the article appear.
I suspect that I mistakenly responded by mail instead of posting a
followup to the net.  Oops.

Agreed, the CRC check would cause a real administrative pain.  All
patches would have to start relative to a known source version, and
would have to be applied strictly in sequence.  That pretty much 
forces patches to be applied in this way distributed by one single
central administrator.

How about another suggestion, then......

I think it is legally permissible to quote portions of a copyrighted
work, up to about ten percent.  That's probably enough to allow
the context-establishing quotes produced by cdiff(1), but not
enough to allow each line of the file-to-be-patched which is to
be deleted or modified to be quoted in the patch file.

How about modifications to cdiff(1) so that instead of literally
quoting each line from the file-to-be-patched which is to be
deleted or modified, it would compute a signature value for those
lines (something like checksum, but less prone to falsing) and
provide that value in the patch file in place of the quoted lines?

patch(1) could then be modified to compute the same signature
value for corresponding lines of the file-to-be-patched, and
alert the user when it detected differences.

-- 
mitchell@mdi.com (Bill Mitchell)