Re: gc and repack ignore .git/*HEAD when checking reachability

From: Duy Nguyen <pclouds@gmail.com>
Date: Jul 12, 2016, 16:13 UTC
Message-ID: <CACsJy8BfXSvKM3=rRCDYzR=rpLRi+FBYs4r1WGXFisq0Esk00w@mail.gmail.com>
In-Reply-To: <20160712155141.GA5967@sigill.intra.peff.net>

On Tue, Jul 12, 2016 at 5:51 PM, Jeff King <peff@peff.net> wrote:

Show 18 quoted lines

> On Tue, Jul 12, 2016 at 05:46:12PM +0200, Duy Nguyen wrote:
>
>> I'm not opposed to letting one worktree see everything, but this move
>> makes it harder to write new scripts (or new builtin commands, even)
>> that works with both single and multiple worktrees because you refer
>> to one ref (in current worktree perspective) differently. If we kill
>> of the main worktree (i.e. git init always creates a linked worktree)
>> then it's less of a problem, but still a nuisance to write
>> refs/worktree/$CURRENT/<something> everywhere.
>
> True. I gave a suggestion for the reading side, but the writing side
> would still remain tedious.
>
> I wonder if, in a worktree, we could simply convert requests to read or
> write names that do not begin with "refs/" as "refs/worktree/$CURRENT/"?
> That makes it a read/write-time alias conversion, but the actual storage
> is just vanilla (so the ref storage doesn't need to care, and
> reachability just works).

A conversion like that is already happening, but it works at git_path() level instead and maps anything outside refs/ to worktrees/$CURRENT. Reorganizing all refs in a single ref storage is probably possible, but...

> The trickiest thing, I think, is FETCH_HEAD, which is not really a
> ref (because it may have a bunch of values, and contain extra
> information).

Yeah.. I think David and Junio touched this when lmdb backend was discussed, which resulted in leaving per-worktree refs to filesystem backend even when shared refs are in lmdb. We probably can still make it work, I think refs subsystem has special case for FETCH_HEAD already. But 'refs' stuff is really not my area, I should stop writing now before making too many wrong statements.

-- 
Duy