git-lfs support

[extrawurst]

I was recently asked if git-lfs is supported.
Research shows that it is not supported out of the box in our upstream libgit2:

• git-lfs#375
• nodegit#914
• libgitsharp2#1236

No idea how git-lfs is implemented in itself but it seems to be a manual job to be supported in gitui.

edit:
seems lfs is using 4 git hooks to work (none of which are currently supported by gitui):

• post-checkout
• post-commit
• post-merge
• pre-push

maybe this can be used as a reference implementation:
https://github.com/Axosoft/nodegit-lfs

[extrawurst]

the libgit2 maintainers keep referring to the filters to implement git-lfs, in order to do this in rust git2-rs needs to support the upstream functions: rust-lang/git2-rs#442

[extrawurst]

here is a another helpful comment on this: libgit2/libgit2#6565 (comment)

[strogonoff]

There’s a tiny LFS compatibility layer I wrote for isomorphic-git: https://github.com/riboseinc/isogit-lfs.

I found it reasonably straightforward to do the following bare minimum needed for our use case:

1. Given a blob, perform an appropriate upload request to LFS server, and get LFS pointer metadata as a response.

2. Serialize received LFS pointer metadata and store it at object’s path in the repository (in place of the original blob).

3. Parse/deserialize LFS pointer metadata stored at an object’s path.

4. Given LFS pointer metadata, perform an appropriate download request to LFS server, and receive a blob as response.

5. Write received blob to a correct LFS cache path in Git directory.

In case of gitui, users would probably expect to be able to check out LFS blobs into working directory, but it wasn’t required in our use case.

[extrawurst]

Ok I only glanced over it right now.

Works in Node runtime only
that is kind of a problem to impose as a dependency for anyone using gitui.

Also I have no idea how to integrate this. Fancy giving me a rough summary?

[strogonoff]

It’s absolutely not suitable for integration here. It was intended for a simpler use case that doesn’t require checking out LFS blobs, for example… Just thought I’d leave it as what I think might be the simplest bare minimum LFS implementation out there (much simpler than nodegit-lfs at any rate) along with the overview of the solution should it come in handy. Feel free to ignore:)