Re: How de-duplicate similar repositories with alternates

On Thu, Nov 29, 2018 at 9:15 PM Ævar Arnfjörð Bjarmason
[off-list ref] wrote:

On Thu, Nov 29 2018, Stefan Beller wrote:

quoted

On Thu, Nov 29, 2018 at 7:00 AM Ævar Arnfjörð Bjarmason
[off-list ref] wrote:

quoted

A co-worker asked me today how space could be saved when you have
multiple checkouts of the same repository (at different revs) on the
same machine. I said since these won't block-level de-duplicate well[1]
one way to do this is with alternates.

Another way is to use git-worktree, which would solve the gc issues
mentioned below?

I view alternates as a historic artefact as the deduping
of objects client side can be done using worktrees, and on the
serverside - I think - most of the git hosters use namespaces
and put a fork network into the same repository and use pack islands.

Can you elaborate on why worktrees would not solve the problem?
(I initially was hesitant to use them as I liked going into .git and tempering
with files such as the config directly. But now I cannot `cd .git` any more;
it turns out the advantages outweigh this corner case that I was attached to)

This was discussed recently on-list & I chimed in with details about
that here:
https://public-inbox.org/git/87po1waqyc.fsf@evledraar.gmail.com/ &
https://public-inbox.org/git/87muwzc2kv.fsf@evledraar.gmail.com/

In particular the "multiple devs" use-case described in the latter
E-Mail is what I have in mind. Worktrees are inherently unsuitable for
that.

Yeah, the separate ref namespace is something I would like to have on
the client side too. I did consider implementing it a couple times but
it's really no small task. Naively, I could achieve that pretty quick
if all refs are loose, but performance would tank once the number of
refs goes over say a hundred.
-- 
Duy