From: Mike Hommey <firstname.lastname@example.org> To: Shawn Pearce <email@example.com> Cc: Jeff King <firstname.lastname@example.org>, git <email@example.com>, David Turner <firstname.lastname@example.org>, Michael Haggerty <email@example.com> Subject: Re: RefTree: Alternate ref backend Date: Fri, 18 Dec 2015 10:36:03 +0900 [thread overview] Message-ID: <20151218013603.GA13717@glandium.org> (raw) In-Reply-To: <CAJo=hJsSgU6yOFZMac85jkOtw9TXWXh0Ext4-Gb1TsSXqROn4g@mail.gmail.com> On Thu, Dec 17, 2015 at 02:28:01PM -0800, Shawn Pearce wrote: > On Thu, Dec 17, 2015 at 2:10 PM, Jeff King <firstname.lastname@example.org> wrote: > > On Thu, Dec 17, 2015 at 01:02:50PM -0800, Shawn Pearce wrote: > > > >> I started playing around with the idea of storing references directly > >> in Git. Exploiting the GITLINK tree entry, we can associate a name to > >> any SHA-1. > > > > Gitlink entries don't imply reachability, though. I guess that doesn't > > matter if your ref backend says "no, really, these are the ref tips, and > > they are reachable". > > Exactly. This works with existing JGit because it swaps out the ref > backend. When GC tries to enumerate the roots (current refs), it gets > these through the ref backend by scanning the tree recursively. The > packer itself doesn't care where those roots came from. > > Same would be true for any other pluggable ref backend in git-core. GC > has to ask the ref backend, and then trust its reply. How/where that > ref backend tracks that is an implementation detail. > > > But you could not push the whole thing up to > > another server and expect it to hold the whole graph. > > Correct, pushing this to another repository doesn't transmit the > graph. If the other repository also used this for its refs backend, > its now corrupt and confused out of its mind. Just like copying the > packed-refs file with scp. Don't do that. :) > > > Which is not strictly necessary, but to me seems like the real advantage > > of using git objects versus some other system. > > One advantage is you can edit HEAD symref remotely. Commit a different > symlink value and push. :) > > I want to say more, but I'm going to hold back right now. There's more > going on in my head than just this. > > > Of course, the lack of reachability has advantages, too. You can > > drop commits pointed to by old reflogs without rewriting the ref > > history. > > Yes. Related thread: "Allowing weak references to blobs and strong references to commits" http://marc.info/?l=git&m=142779648816577&w=2 Mike
next prev parent reply other threads:[~2015-12-18 2:19 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-12-17 21:02 Shawn Pearce 2015-12-17 21:57 ` Junio C Hamano 2015-12-17 22:15 ` Shawn Pearce 2015-12-17 22:10 ` Jeff King 2015-12-17 22:28 ` Shawn Pearce 2015-12-18 1:36 ` Mike Hommey [this message] 2015-12-22 15:41 ` Michael Haggerty 2015-12-22 16:11 ` Shawn Pearce 2015-12-22 17:04 ` Dave Borowitz 2015-12-22 17:17 ` Michael Haggerty 2015-12-22 18:50 ` Shawn Pearce 2015-12-22 19:09 ` Junio C Hamano 2015-12-22 19:11 ` Shawn Pearce 2015-12-22 19:34 ` Junio C Hamano 2015-12-23 4:59 ` Michael Haggerty 2015-12-24 1:33 ` Junio C Hamano [not found] ` <4689734.cEcQ2vR0aQ@mfick1-lnx> 2015-12-22 20:56 ` Martin Fick 2015-12-22 21:23 ` Junio C Hamano
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