From: "Ævar Arnfjörð Bjarmason" <avarab@gmail•com>
To: "Robert P. J. Day" <rpjday@crashcourse•ca>
Cc: Git Mailing list <git@vger•kernel.org>
Subject: Re: easy way to demonstrate length of colliding SHA-1 prefixes?
Date: Sun, 02 Dec 2018 14:23:56 +0100 [thread overview]
Message-ID: <87y398uknn.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.21.1812020647440.32023@localhost.localdomain>
On Sun, Dec 02 2018, Robert P. J. Day wrote:
> as part of an upcoming git class i'm delivering, i thought it would
> be amusing to demonstrate the maximum length of colliding SHA-1
> prefixes in a repository (in my case, i use the linux kernel git repo
> for most of my examples).
>
> is there a way to display the objects in the object database that
> clash in the longest object name SHA-1 prefix; i mean, short of
> manually listing all object names, running that through cut and sort
> and uniq and ... you get the idea.
>
> is there a cute way to do that? thanks.
You'll always need to list them all. It's inherently an operation where
for each SHA-1 you need to search for other ones with that prefix up to
a given length.
Perhaps you've missed that you can use --abbrev=N for this, and just
grep for things that are loger than that N, e.g. for linux.git:
git log --oneline --abbrev=10 --pretty=format:%h |
grep -E -v '^.{10}$' |
perl -pe 's/^(.{10}).*/$1/'
This will list the 4 objects that need more than 10 characters to be
shown unambiguously. If you then "git cat-file -t" them you'll get the
disambiguation help.
next prev parent reply other threads:[~2018-12-02 13:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-02 11:50 easy way to demonstrate length of colliding SHA-1 prefixes? Robert P. J. Day
2018-12-02 13:23 ` Ævar Arnfjörð Bjarmason [this message]
2018-12-02 16:24 ` Robert P. J. Day
2018-12-03 22:30 ` Matthew DeVore
2018-12-03 22:57 ` Jeff King
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