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Date:	Fri, 8 Jul 2016 15:25:04 -0400
From:	Theodore Ts'o <tytso@mit.edu>
To:	Junio C Hamano <gitster@pobox.com>
Cc:	Josh Triplett <josh@joshtriplett.org>, git@vger.kernel.org
Subject: Re: gc and repack ignore .git/*HEAD when checking reachability
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On Fri, Jul 08, 2016 at 10:14:33AM -0700, Junio C Hamano wrote:
> 
> It cannot be "anything directly under .git that has all-caps name
> that ends with _HEAD".  The ones we write we know are going to be
> removed at some point in time (e.g. "git reset", "git bisect reset",
> "git merge --abort", etc.).  We do not have any control on random
> ones that the users and third-party tools leave behind, holding onto
> irrelevant objects forever.

What about anything that is all-caps and ends in _HEAD which has a
mod-time within the last N days?  (Where N is 2-7 days.)  If it's
older than that, it's almost certainly stale...

						- Ted