From: Jonathan Nieder <jrnieder@gmail.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: Stefan Beller <sbeller@google.com>, git <git@vger.kernel.org>,
Junio C Hamano <gitster@pobox.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Edward Thomson <ethomson@edwardthomson.com>,
"brian m. carlson" <sandals@crustytoothpaste.net>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>,
demerphq <demerphq@gmail.com>,
Brandon Williams <bmwill@google.com>,
Derrick Stolee <stolee@gmail.com>, Jeff King <peff@peff.net>
Subject: Re: How is the ^{sha256} peel syntax supposed to work?
Date: Wed, 29 Aug 2018 12:12:32 -0700 [thread overview]
Message-ID: <20180829191232.GC7547@aiede.svl.corp.google.com> (raw)
In-Reply-To: <87zhx5c8wo.fsf@evledraar.gmail.com>
Hi,
Ævar Arnfjörð Bjarmason wrote:
> On Wed, Aug 29 2018, Jonathan Nieder wrote:
>> what objects would you expect the following to refer to?
>>
>> abcdabcd^{sha1}
>> abcdabcd^{sha256}
>> ef01ef01^{sha1}
>> ef01ef01^{sha256}
>
> I still can't really make any sense of why anyone would even want #2 as
> described above, but for this third case I think we should do this:
>
> abcdabcd^{sha1} = abcdabcdabcdabcdabcdabcdabcdabcdabcdabcd
> abcdabcd^{sha256} = ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01
> ef01ef01^{sha1} = ef01ef01ef01ef01ef01ef01ef01ef01ef01ef01
> ef01ef01^{sha256} = abcdabcdabcdabcdabcdabcdabcdabcdabcdabcd...
>
> I.e. a really useful thing about this peel syntax is that it's
> forgiving, and will try to optimistically look up what you want.
Sorry, I'm still not understanding.
I am not attached to any particular syntax, but what I really want is
the following:
Someone who only uses SHA-256 sent me the commit id
abcdabcdabcdabcdabcdabcdabcdabcdabcdabcd... out of band.
Show me that commit.
I don't care what object id you show me when you show that
commit. If I pass --output-format=sha1, then that means I
care, and show me the SHA-1.
In other words, I want the input format and output format completely
decoupled. If I pass ^{sha1}, I am indicating the input format. To
specify the output format, I'd use --output-format instead.
That lets me mix both hash functions in my input:
git --output-format=sha256 diff abcdabcd^{sha1} abcdabcd^{sha256}
I learned about these two commits out of band from different users,
one who only uses SHA-1 and the other who only uses SHA-256.
In other words:
[...]
> Similarly, I think it would be very useful if we just make this work:
>
> git rev-parse $some_hash^{sha256}^{commit}
>
> And not care whether $some_hash is SHA-1 or SHA-256, if it's the former
> we'd consult the SHA-1 <-> SHA-256 lookup table and go from there, and
> always return a useful value.
The opposite of this. :)
Thanks,
Jonathan
next prev parent reply other threads:[~2018-08-29 19:12 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 14:02 Questions about the hash function transition Ævar Arnfjörð Bjarmason
2018-08-23 14:27 ` Junio C Hamano
2018-08-23 15:20 ` Ævar Arnfjörð Bjarmason
2018-08-23 16:13 ` Junio C Hamano
2018-08-24 1:40 ` brian m. carlson
2018-08-24 1:54 ` Jonathan Nieder
2018-08-24 4:47 ` brian m. carlson
2018-08-24 4:52 ` Jonathan Nieder
2018-08-24 1:47 ` Jonathan Nieder
2018-08-28 12:04 ` Johannes Schindelin
2018-08-28 12:49 ` Derrick Stolee
2018-08-28 17:12 ` Jonathan Nieder
2018-08-28 17:11 ` Jonathan Nieder
2018-08-29 13:09 ` Johannes Schindelin
2018-08-29 13:27 ` Derrick Stolee
2018-08-29 14:43 ` Derrick Stolee
2018-08-29 9:13 ` How is the ^{sha256} peel syntax supposed to work? Ævar Arnfjörð Bjarmason
2018-08-29 17:51 ` Stefan Beller
2018-08-29 17:59 ` Jonathan Nieder
2018-08-29 18:34 ` Stefan Beller
2018-08-29 18:41 ` Ævar Arnfjörð Bjarmason
2018-08-29 19:12 ` Jonathan Nieder [this message]
2018-08-29 19:37 ` Ævar Arnfjörð Bjarmason
2018-08-29 20:46 ` Jonathan Nieder
2018-08-29 23:45 ` Jeff King
2018-08-29 20:53 ` Junio C Hamano
2018-08-29 21:01 ` Jonathan Nieder
2018-08-29 17:56 ` Jonathan Nieder
2018-08-24 2:51 ` Questions about the hash function transition Jonathan Nieder
2018-08-28 13:50 ` Ævar Arnfjörð Bjarmason
2018-08-28 14:15 ` Edward Thomson
2018-08-28 15:02 ` Ævar Arnfjörð Bjarmason
2018-08-28 15:45 ` Junio C Hamano
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