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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Wed, 6 Dec 2023 08:45:30 +0100
Message-ID: <CAMuHMdUqASMMmLOjFerMncm2EjNn22GHr9_2oq=oPX91ar_sBA@mail.gmail.com>
Subject: Re: [PATCH] checkpatch: Also accept commit ids with 13-40 chars of sha1
To:     Joe Perches <joe@perches.com>
Cc:     =?UTF-8?Q?Niklas_S=C3=B6derlund?= <niklas.soderlund@ragnatech.se>,
        Andy Whitcroft <apw@canonical.com>,
        Dwaipayan Ray <dwaipayanray1@gmail.com>,
        Lukas Bulwahn <lukas.bulwahn@gmail.com>,
        Louis Peens <louis.peens@corigine.com>,
        Simon Horman <horms@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Junio C Hamano <gitster@pobox.com>,
        linux-kernel@vger.kernel.org
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Hi Joe,

On Tue, Dec 5, 2023 at 9:05 PM Joe Perches <joe@perches.com> wrote:
> On Tue, 2023-12-05 at 20:34 +0100, Geert Uytterhoeven wrote:
> > Documentation/dev-tools/checkpatch.rst says:
> >
> >   **GIT_COMMIT_ID**
> >     The proper way to reference a commit id is:
> >     commit <12+ chars of sha1> ("<title line>")
>
> It's not just checkpatch.
>
> Documentation/process/submitting-patches.rst:``git bisect``, please use the 'Fixes:' tag with the first 12 characters of
>
>
> So that would need to be updated as well.

And:

Documentation/process/maintainer-tip.rst: - Fixes: 12char-SHA1
("sub/sys: Original subject line")

but the example uses 15:

Documentation/process/maintainer-tip.rst:     Fixes: abcdef012345678
("x86/xxx: Replace foo with bar")

Documentation/process/researcher-guidelines.rst:  Fixes:
aaaabbbbccccdddd ("Introduce support for FooBar")

16

Documentation/process/submitting-patches.rst:   Commit
e21d2170f36602ae2708 ("video: remove unnecessary

20

> And 12 still has quite some headroom.
>
> $ git rev-list --all --abbrev=0 --abbrev-commit | \
>   awk '{ a[length] += 1 } END { for (len in a) print len, a[len] }'
> 5 107
> 6 684276
> 7 505734
> 8 41769
> 9 2665
> 10 174
> 11 8

How many collisions do you need? These will be dereferenced years
from now.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds