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From: Junio C Hamano <gitster@pobox.com>
To: "SZEDER Gábor" <szeder.dev@gmail.com>,
	"brian m. carlson" <sandals@crustytoothpaste.net>
Cc: "Đoàn Trần Công Danh" <congdanhqx@gmail.com>,
	git@vger.kernel.org, "Jeff King" <peff@peff.net>
Subject: Re: [PATCH v3 2/2] diff: index-line: respect --abbrev in object's name
Date: Fri, 14 Aug 2020 10:00:53 -0700	[thread overview]
Message-ID: <xmqqwo21xiuy.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <20200814151815.GA29528@szeder.dev> ("SZEDER =?utf-8?Q?G?= =?utf-8?Q?=C3=A1bor=22's?= message of "Fri, 14 Aug 2020 17:18:15 +0200")

SZEDER Gábor <szeder.dev@gmail.com> writes:

>> +diff --git a/file0 b/file0
>> +new file mode 100644
>> +index 0000000000000000000000000000000000000000..01e79c32a8c99c557f0757da7cb6d65b3414466d
>> +--- /dev/null
>> ++++ b/file0
>> +@@ -0,0 +1,3 @@
>> ++1
>> ++2
>> ++3
>> +diff --git a/file2 b/file2
>> +new file mode 100644
>> +index 0000000000000000000000000000000000000000..01e79c32a8c99c557f0757da7cb6d65b3414466d
>> +--- /dev/null
>> ++++ b/file2
>> +@@ -0,0 +1,3 @@
>> ++1
>> ++2
>> ++3
>> +$
>
> All these new tests break when run with GIT_TEST_DEFAULT_HASH=sha256
> with something like:
>
>   + test_cmp expect actual
>   --- expect	2020-08-14 15:05:12.209285397 +0000
>   +++ actual	2020-08-14 15:05:12.205285279 +0000
>   @@ -2,7 +2,7 @@
>    0000000000000000000000000000000000000000000000000000000000000000
>    diff --git a/dir/sub b/dir/sub
>    new file mode ffff44
>   -index ffffffffff..fffffffa79
>   +index ffffffffff..fffffff895

Ouch.  These apparently come from

process_diffs () {
	_x04="[0-9a-f][0-9a-f][0-9a-f][0-9a-f]" &&
	_x07="$_x05[0-9a-f][0-9a-f]" &&
	sed -e "s/$OID_REGEX/$ZERO_OID/g" \
	    -e "s/From $_x40 /From $ZERO_OID /" \
	    -e "s/from $_x40)/from $ZERO_OID)/" \
	    -e "s/commit $_x40\$/commit $ZERO_OID/" \
	    -e "s/commit $_x40 (/commit $ZERO_OID (/" \
	    -e "s/$_x40 $_x40 $_x40/$ZERO_OID $ZERO_OID $ZERO_OID/" \
	    -e "s/$_x40 $_x40 /$ZERO_OID $ZERO_OID /" \
	    -e "s/^$_x40 $_x40$/$ZERO_OID $ZERO_OID/" \
	    -e "s/^$_x40 /$ZERO_OID /" \
	    -e "s/^$_x40$/$ZERO_OID/" \
	    -e "s/$_x07\.\.$_x07/fffffff..fffffff/g" \
	    -e "s/$_x07,$_x07\.\.$_x07/fffffff,fffffff..fffffff/g" \
	    -e "s/$_x07 $_x07 $_x07/fffffff fffffff fffffff/g" \
	    -e "s/$_x07 $_x07 /fffffff fffffff /g" \
	    -e "s/Merge: $_x07 $_x07/Merge: fffffff fffffff/g" \
	    -e "s/$_x07\.\.\./fffffff.../g" \
	    -e "s/ $_x04\.\.\./ ffff.../g" \
	    -e "s/ $_x04/ ffff/g" \
	    "$1"
}

Hash-independence may be good, but it should not munge expected mode
bits from 100644 to ffff44, which I think is a bug in the original
introduced in 72f936b1 (t4013: make test hash independent,
2020-02-07).

When we are adjusting the abbrev length of the index line, of course
$_x07 would not be sufficient to match the abbreviated object name
in full, so a79 vs 895 can be explained and is a bug in this patch
that did not update the process_diffs helper.

Another thing that I find somewhat problematic in the original
(brian cc'ed) is that it does not special case all-zero object name
specially.  By turning any and all instances of $_x40 to $ZERO_OID,
we lose the distinction between a random-looking object name which
got turned into $ZERO_OID by the processing, and an object name that
was $ZERO_OID from the beginning, so we won't catch a possible
future bug where new file's preimage object name is not $ZERO_OID
(this is plausible when you try to show an intent-to-add entry; the
diff between the index and the working tree would be "new file"
patch, but the index entry records the object name for an empty
blob, e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 instead of $ZERO_OID
can easily be emitted by a mistaken implementation).

  reply	other threads:[~2020-08-14 17:01 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-09  2:19 [RFC PATCH 0/2] extend --abbrev support to diff-patch format Đoàn Trần Công Danh
2020-08-09  2:19 ` [RFC PATCH 1/2] revision: differentiate if --no-abbrev asked explicitly Đoàn Trần Công Danh
2020-08-09  2:19 ` [RFC PATCH 2/2] diff: extend --abbrev support to diff-patch format Đoàn Trần Công Danh
2020-08-09 19:01 ` [RFC PATCH 0/2] " Junio C Hamano
2020-08-10 10:00   ` Jeff King
2020-08-10 12:31     ` Đoàn Trần Công Danh
2020-08-10 15:15       ` Junio C Hamano
2020-08-10 15:27         ` Jeff King
2020-08-11  0:33           ` Đoàn Trần Công Danh
2020-08-11  5:22             ` Jeff King
2020-08-11 12:07               ` Đoàn Trần Công Danh
2020-08-10 15:06     ` Junio C Hamano
2020-08-11 11:49 ` [PATCH v2 0/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-11 11:49   ` [PATCH v2 1/2] revision: differentiate if --no-abbrev asked explicitly Đoàn Trần Công Danh
2020-08-11 18:54     ` Junio C Hamano
2020-08-11 11:49   ` [PATCH v2 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-14  0:23 ` [PATCH v3 0/2] " Đoàn Trần Công Danh
2020-08-14  0:23   ` [PATCH v3 1/2] revision: differentiate if --no-abbrev asked explicitly Đoàn Trần Công Danh
2020-08-14  0:50     ` Junio C Hamano
2020-08-14  0:59       ` Đoàn Trần Công Danh
2020-08-14  1:06         ` Junio C Hamano
2020-08-14 14:50           ` Đoàn Trần Công Danh
2020-08-19 22:50             ` Junio C Hamano
2020-08-14  0:23   ` [PATCH v3 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-14 15:18     ` SZEDER Gábor
2020-08-14 17:00       ` Junio C Hamano [this message]
2020-08-14 18:59         ` Junio C Hamano
2020-08-15  0:21           ` brian m. carlson
2020-08-15  2:27             ` Đoàn Trần Công Danh
2020-08-17 16:17               ` Junio C Hamano
2020-08-20  4:56               ` Junio C Hamano
2020-08-20 12:35 ` [PATCH v4 0/2] " Đoàn Trần Công Danh
2020-08-20 12:35   ` [PATCH v4 1/2] t4013: improve diff-post-processor logic Đoàn Trần Công Danh
2020-08-20 19:49     ` Junio C Hamano
2020-08-21 12:05       ` Đoàn Trần Công Danh
2020-08-21 15:44         ` Junio C Hamano
2020-08-20 12:35   ` [PATCH v4 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-20 19:58     ` Junio C Hamano
2020-08-21 11:51 ` [PATCH v5 0/2] " Đoàn Trần Công Danh
2020-08-21 11:51   ` [PATCH v5 1/2] t4013: improve diff-post-processor logic Đoàn Trần Công Danh
2020-08-21 11:51   ` [PATCH v5 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh

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