Fetch pyproject.toml from GitHub API

[charliermarsh]

Summary

When resolving Git metadata, we may be able to fetch the metadata from GitHub directly in some cases. This is way faster, since we don't need to perform many Git operations and, in particular, don't need to clone the repo.

This only works in the following cases:

• The Git repository is public. Otherwise, I believe you need an access token, which we don't have.
• The pyproject.toml has static metadata.
• The pyproject.toml has no tool.uv.sources. Otherwise, we need to lower them... And, if there are any paths or workspace sources, that requires an install path (i.e., we need the content on-disk).
• The project is in the repo root. If it's in a subdirectory, it could be a workspace member. And if it's a workspace member, there could be sources defined in the workspace root. But we can't know without fetching the workspace root -- and we need the workspace in order to find the root...

Closes #10568.

[zanieb]

Did you do any benches?

[charliermarsh]

Yeah, I think it's just whatever the cost of cloning the repo is. For example, >20x faster for uv:

❯ hyperfine 'echo "uv @ git+https://github.com/astral-sh/uv" | ./target/release/uv pip compile - -n' 'echo "uv @ git+https://github.com/astral-sh/uv" | uv pip compile - -n' --warmup 5 --runs 10
Benchmark 1: echo "uv @ git+https://github.com/astral-sh/uv" | ./target/release/uv pip compile - -n
  Time (mean ± σ):     126.7 ms ±  13.6 ms    [User: 27.9 ms, System: 12.3 ms]
  Range (min … max):   113.7 ms … 162.6 ms    10 runs

Benchmark 2: echo "uv @ git+https://github.com/astral-sh/uv" | uv pip compile - -n
  Time (mean ± σ):      2.892 s ±  0.035 s    [User: 1.220 s, System: 0.389 s]
  Range (min … max):    2.840 s …  2.942 s    10 runs

Summary
  echo "uv @ git+https://github.com/astral-sh/uv" | ./target/release/uv pip compile - -n ran
   22.83 ± 2.46 times faster than echo "uv @ git+https://github.com/astral-sh/uv" | uv pip compile - -n

(Python interpreter querying is like 40ms out of that 120ms. The GitHub API call is like 50ms. The GitHub file fetch is like 30ms.)

[konstin]

We should set a good example and add contact information and version too: uv/{uv_version} (+https://github.com/astral-sh/uv)

[charliermarsh]

I'll change this separately, since we already do this in uv-git.

[konstin]

We need a log statement with the error here

[konstin]

How do we handle github api limits? If I'm reading the header correctly we get 60 requests per hour. Do we just rely on github to send us 403 when we've exhausted the rate limit?

[charliermarsh]

Yes. It’s no different than the existing fast-path code we have in the Git crate.