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From: Jeff King <>
To: "Michal Suchánek" <>
Cc: "Ævar Arnfjörð Bjarmason" <>,
	"ZheNing Hu" <>,
	"Git List" <>,
	"Junio C Hamano" <>,
	"Christian Couder" <>,, "Taylor Blau" <>
Subject: Re: Question: How to execute git-gc correctly on the git server
Date: Thu, 8 Dec 2022 20:37:04 -0500	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, Dec 09, 2022 at 01:49:18AM +0100, Michal Suchánek wrote:

> > In this case it's the mtime on the object file (or the pack containing
> > it). But yes, it is far from a complete race-free solution.
> So if you are pushing a branch that happens to reuse commits or other
> objects from an earlier branh that might have been collected ín the
> meantime you are basically doomed.

Basically yes. We do "freshen" the mtimes on object files when we omit
an object write (e.g., your index state ends up at the same tree as an
old one). But for a push, there is no freshening. We check the graph at
the time of the push and decide if we have everything we need (either
newly pushed, or from what we already had in the repo). And that is
what's racy; somebody might be deleting as that check is happening.

> People deleting a branch and then pushing another variant in which many
> objects are the same is a risk.
> People exporting files from somewhere and adding them to the repo which
> are bit-identical when independently exported by multiple people and
> sometimes deleting branches is a risk.

Yes, both of those are risky (along with many other variants).


  reply	other threads:[~2022-12-09  1:37 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-07 15:58 Question: How to execute git-gc correctly on the git server ZheNing Hu
2022-12-07 23:57 ` Ævar Arnfjörð Bjarmason
2022-12-08  1:16   ` Michal Suchánek
2022-12-08  7:01     ` Jeff King
2022-12-09  0:49       ` Michal Suchánek
2022-12-09  1:37         ` Jeff King [this message]
2022-12-09  7:26           ` ZheNing Hu
2022-12-09 13:48             ` Ævar Arnfjörð Bjarmason
2022-12-11 16:01               ` ZheNing Hu
2022-12-11 16:27                 ` Michal Suchánek
2022-12-09  7:15     ` ZheNing Hu
2022-12-08  6:59   ` Jeff King
2022-12-08 12:35     ` Ævar Arnfjörð Bjarmason
2022-12-14 20:11       ` Taylor Blau

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