Re: Exec upload-pack on remote with what parameters to get direntries.

[Jeff King <peff@peff.net>]

On Sat, Aug 28, 2021 at 02:56:17PM +0200, Stef Bon wrote:

> I've got a custom ssh library which I use to make a connection to a
> git server like www.github.com, user stefbon.
> 
> Now I want to get the direntries of a remote repo, and I know I have
> to use upload-pack for that, but with what parameters?
> 
> I want to use the outcome to make a fuse fs, user can browse the
> files. Possibly the user can also view the contents.

The protocol used by upload-pack is described in
Documentation/technical/pack-protocol.txt, but in short: I don't think
it will do what you want.

There is no operation to list the tree contents, for example, nor really
even a good way to fetch a single object. The protocol is geared around
efficiently transferring slices of history, so it is looking at sets of
reachable objects (what the client is asking for, and what it claims to
have).

You might be able to cobble something together with shallow and partial
fetches. E.g., something like:

  git clone --depth 1 --filter=blob:none --single-branch -b $branch

is basically asking to send only a single commit, plus all of its trees,
but no blobs. From there you could parse the tree objects to assemble a
directory listing. Possibly with a tree:depth filter you could even do
it iteratively.

Some hosts offer a separate API that would give you a much nicer
interface. E.g., GitHub has:

  https://docs.github.com/en/rest/reference/git#trees

But of course that won't work with GitLab, etc, and you'd have to
implement against the API for each hosting provider.

-Peff