On Wed, Oct 21, 2020 at 07:10:02PM +0200, Alexandr Miloslavskiy wrote: > We currently do not intend to use '--filter=tree:0' ourself, but we are > trying to support all kinds of user repositories with our UI. So we > basically have these choices: > > A) Declare '--filter=tree:0' repos as completely wrong and unsupported > in out UI, also giving an option to "un-partial" them. > > B) Support '--filter=tree:0' repos, but don't support operations such > as blame and file log > > C) Use some magic to efficiently download objects that will be needed > for a command such as Blame, while keeping the rest of the repository > partial. This is where the command described in (3) will help a lot. > > We would of course prefer (C) if it's reasonably possible. (C) is probably the most reasonable. If you have a promisor remote which is missing objects, running 'git blame' etc. will transparently download whatever objects it is missing. > Unfortunately this does not work as expected. Try the following steps: > > A) Clone repo with '--filter=tree:0' > $ git clone --bare --filter=tree:0 --branch master > https://github.com/git/git.git > > B) Change filter to 'blob:none' > $ cd git.git > $ git config remote.origin.partialclonefilter 'blob:none' > > C) fetch > $ git fetch origin > Note that there is no 'Receiving objects:' output. Ah; I would have thought that the server would have sent objects, even though we have lots of 'have' lines, since we are treating the server as a promisor remote and might not have the full reachability closure over the haves. Jonathan Tan knows better than I do here. Maybe he could chime in. > > I think what you probably want is a step 1.5 to tell Git "I'm not going > > to ask for or care about the entirety of my working copy, I really just > > want objects in path...", and you can do that with sparse checkouts. See > > https://git-scm.com/docs/git-sparse-checkout for more. > > For simplicity of discussion, let's focus on the problem of running > Blame efficiently in a repo that was cloned with '--filter=tree:0'. In > order to blame file '/1/2/Foo.txt', we will need the following: > > * Trees '/1' > * Trees '/1/2' > * Blobs '/1/2/Foo.txt' > > All of these will be needed to unknown commit depth. For simplicity, > the proposed command will download these for all commits. Specifying > a range of revisions could be nice, but I feel that it's not worth the > complexity. > > Correct me if I'm wrong: I think that sparse checkout will not help to > achieve the goal? I see what you're saying. Here sparse-checkout and partial clones confusingly diverge: what you really want is to say "I want all of the objects that I need to construct this directory at any point in history" so that you can run "git blame" on some path within that directory without the need for a follow-up fetch. > This is why I suggest a command that will accept paths and send > requested objects, also forcing server to assume that all of them are > missing in client's repository. In any case the '--filter=sparse:<oid>' bit is not recommended for use, but perhaps this is a convincing use-case. I didn't follow the partial clone development close enough to know whether this has already been discussed, but I'm sure that it has. Thanks, Taylor
