Re: [RFH] Exploration of an alternative diff_delta() algorithm

From: Nicolas Pitre <nico@cam.org>
Date: Apr 9, 2006, 17:14 UTC
Message-ID: <Pine.LNX.4.64.0604091307460.2215@localhost.localdomain>
In-Reply-To: <20060409143117.GA23908@erlang.gbar.dtu.dk>

On Sun, 9 Apr 2006, Peter Eriksen wrote:

Show 38 quoted lines

> Greetings Gitlings,
> 
> I've been trying to implement an alternative algorithm
> for diff_delta().  I'm getting close to something that
> works, but now I'm stuck!  I think it has something to
> do with pack-objects.c, but I'm not sure.  Here's the
> first test that fails:
> 
> *** t5500-fetch-pack.sh ***
> * FAIL 1: 1st pull
>         git-fetch-pack -v .. B A > log.txt 2>&1
> * FAIL 2: fsck
>         git-fsck-objects --full > fsck.txt 2>&1
> * FAIL 3: new object count after 1st pull
>         test 33 = 0
> * FAIL 4: minimal count
>         test 33 = 0
> * FAIL 5: repack && prune-packed in client
>         (git-repack && git-prune-packed)2>>log.txt
> *   ok 5: 2nd pull
> *   ok 6: fsck
> * FAIL 7: new object count after 2nd pull
>         test 192 = 198
> * FAIL 8: minimal count
>         test 192 = 198
> * FAIL 9: repack && prune-packed in client
>         (git-repack && git-prune-packed)2>>log.txt
> *   ok 9: 3rd pull
> *   ok 10: fsck
> * FAIL 11: new object count after 3rd pull
>         test 3 = 228
> * FAIL 12: minimal count
>         test 3 = 30
> * failed 8 among 12 test(s)
> 
> I've been looking all around the current diff_delta(), and I
> can't see, what I'm missing.  Any ideas?  The file is meant to
> replace the current diff-delta.c.

Nothing outside diff-delta.c and patch-delta.c is aware of the delta data format. So if your version is meant to be a transparent replacement then it should pass all tests. If it doesn't then it is broken.

To help you play around you could try the test-delta utility (make test-delta to build it).

So:

	test-delta -d file1 file2 delta_file
	test-delta -p file1 delta_file file3
	cmp file2 file3

You should always have file3 identical to file2.

Nicolas