Re: "There are too many unreachable loose objects" - why don't we run 'git prune' automatically?

From: Jeff King <peff@peff.net>
Date: Jun 9, 2017, 05:27 UTC
Message-ID: <20170609052755.dsuqd4gizi2opoya@sigill.intra.peff.net>
In-Reply-To: <9C2F2EA2-0C59-4EA2-8C8E-10228FB82D90@gmail.com>

On Thu, Jun 08, 2017 at 02:45:48PM +0200, Lars Schneider wrote:

Show 10 quoted lines

> I recently ran into "There are too many unreachable loose objects; run 
> 'git prune' to remove them." after a "Auto packing the repository in 
> background for optimum performance." message.
> 
> This was introduced with a087cc9 "git-gc --auto: protect ourselves from 
> accumulated cruft" but I don't understand the commit message really.
> 
> Why don't we call 'git prune' automatically? I though Git would prune
> unreachable objects after 90 days by default anyways. Is the warning 
> about unreachable objects that are not yet 90 days old?

We _do_ call "git prune", but we do so with whatever configured expiration time is (by default 2 weeks; the 90-day expiration is for reflogs).

The problem is that auto-gc kicked in because there were a bunch of loose objects, but after repacking and running "git prune" there were still enough loose objects to trigger auto-gc. Which means every command you run will do an auto-gc that never actually helps.

So you have two options:

  1. Wait until those objects expire (which may be up to 2 weeks,
     depending on how recent they are), at which point your auto-gc will
     finally delete them.

  2. Run "git prune". Without an argument it prunes everything now,
     with no expiration period.

I agree the existing message isn't great. There should probably be a big advise() block explaining what's going on (and that expert users can disable).

-Peff