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From: "Ævar Arnfjörð Bjarmason" <>
To: Junio C Hamano <>
Cc: Konstantin Ryabitsev <>,
Subject: Re: The most efficient way to test if repositories share the same objects
Date: Thu, 22 Mar 2018 20:53:57 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, Mar 22 2018, Junio C. Hamano wrote:

> Ævar Arnfjörð Bjarmason <> writes:
>> But of course that'll just give you the tips. You could then use `git
>> cat-file --batch-check` on both ends to see what commits from the other
>> they report knowing about, in case they have branches that are
>> ahead/behind the other.
> I am not sure how you are envisioning to use "cat-file
> --batch-check" here.  Do you mean to take "rev-list --all" output
> from both and compare, or something?

By doing something like this:

        cd /tmp &&
        git clone gitster-git;
        git clone avar-git;
        git -C gitster-git for-each-ref --format="%(object)" | git -C avar-git cat-file --batch-check|grep -E -o '(commit|missing)'|sort|uniq -c &&
        git -C avar-git for-each-ref --format="%(object)" | git -C gitster-git cat-file --batch-check|grep -E -o '(commit|missing)'|sort|uniq -c

Which outputs:

    673 commit
    696 missing
    374 commit
    495 missing

Which of course, as noted, isn't going to be a good general solution in
all cases, but it's blindingly fast, and since the original question is
essentially that he's starting out with doing a rough equivalent of
that, but for tags only, maybe it'll work for his use-case.

> I am not sure how Konstantin defines "the most efficient", but if it
> is "with the smallest number of bits exchanged between the
> repositories", then the answer would probably be to find the root
> commit(s) in each repository and if they share any common root(s).
> If there isn't then there is no hope to share objects between them,
> of course.

Yes, that would probably be much better:

    diff -ru <(git -C avar-git log --oneline --pretty=format:%H --max-parents=0) \
             <(git -C gitster-git log --oneline --pretty=format:%H --max-parents=0) &&

  reply	other threads:[~2018-03-22 19:54 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-22 16:48 The most efficient way to test if repositories share the same objects Konstantin Ryabitsev
2018-03-22 19:20 ` Ævar Arnfjörð Bjarmason
2018-03-22 19:35   ` Junio C Hamano
2018-03-22 19:53     ` Ævar Arnfjörð Bjarmason [this message]
2018-03-22 21:32     ` Konstantin Ryabitsev
2018-03-22 21:44       ` Junio C Hamano
2018-03-23 13:57         ` Konstantin Ryabitsev
2018-03-23 14:36           ` Ævar Arnfjörð Bjarmason

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