Progress information in working copy checkout

[olsen232]

There's no indication when sno push, pull, or clone might be done.

Underlying git commands support this so a fix will be reasonably straightforward.

[olsen232]

@rcoup wrote:

Most git-fetch/git-push output isn't really useful for anyone IMO (counting/enumerating what?). Pygit2 remotes have a whole callback setup, I would prefer to use that and output something sensible for us, and for machine-readable maybe jsonl to stderr with the raw TransferProgress stats & sideband_progress info?

In the meantime I think it's probably ok, we can always rework the output further down the track.

[olsen232]

We also need to report progress when writing / rewriting working copies, since that can take an even longer

[rcoup]

Using submodules introduces more complexities, since they're fetched in parallel normally. Not sure whether that applies to subtrees too.

[craigds]

In 6d08db3c094164c61b57c7123dc7696cbb575375 I added usable progress for working copy checkouts. It's not pretty (at all), and you have to use sno -v checkout to get the logger to show up, but it's machine readable at least.

IMO we should implement progress ourselves via pygit2 rather than call git commands in a subprocess. That way we can do something consistent across different commands.

[hamishcampbell]

This can probably be closed. We have good progress information now for clones, working copy creation, as well as LFS push/pull.