On Wednesday, January 29, 2020 3:12:59 AM MST Jeff King wrote: > On Tue, Jan 28, 2020 at 08:36:53AM -0700, Martin Fick wrote: > > > There's a slight downside in that tools which _aren't_ careful about > > > repositoryformatversion might try to operate on the repository, writing > > > into refs/ or whatever. But such tools are broken, and I'm not sure we > > > should be catering to them (besides which, the packed-refs ship sailed > > > long ago, so they're already potentially dangerous). > > > > Could you elaborate on this a bit because it seems on the surface that > > these tools aren't very dangerous, and therefore likely many of them > > exist? > > > > What are the dangers today of tools that understand/operate on loose and > > packed refs without reading repositoryformatversion? > > I was mostly thinking of hacky scripts that tried to touch .git/refs > directly. And there are a few levels of dangerous there: > > - if you're doing "echo $sha1 >.git/refs/heads/master", then you're > not locking properly. But it would probably work most of the time. > > - if you're properly taking a lock on ".git/refs/heads/master.lock" > and renaming into place but not looking at packed-refs, then you > might overwrite somebody else's update which is in the packed file > > - if you're trying to read refs and not reading packed-refs, obviously > you might miss some values > > If you're actually doing the correct locking and packed-refs read (which > "real" implementations like libgit2 do) then no, I don't think that's > dangerous. And I think libgit2 properly complains when it sees a > repositoryformatversion above 0. I don't know offhand about JGit, or any > of the lesser-used ones like dulwich or go-git. Today, some of these sound like shortcuts that are very likely taken quite a bit by cleanup and other maintenance scripts (not necessarily formal git tools), and the impact of these shortcuts is likely low with the current model. However, I suspect these tools/scripts could be seriously disruptive if we leave the refs dir around when using reftable, -Martin -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
