Very basic source distribution support. What's included:
- Include and exclude patterns (hard-coded): Currently, we have
globset+walkdir in one part and glob in the other. I'll migrate
everything to globset+walkset and some custom perf optimizations to
avoid traversing irrelevant directories on top. I'll also pick a glob
syntax (or subset), PEP 639 seems like a good candidate since it's
consistent with what we already have to support.
- Add the `PKG-INFO` file with metadata: Thanks to Code Metadata 2.2,
this metadata is reliable and can be read statically by external tools.
Example output:
```
$ tar -ztvf dist/dummy-0.1.0.tar.gz
-rw-r--r-- 0/0 154 1970-01-01 01:00 dummy-0.1.0/PKG-INFO
-rw-rw-r-- 0/0 509 1970-01-01 01:00 dummy-0.1.0/pyproject.toml
drwxrwxr-x 0/0 0 1970-01-01 01:00 dummy-0.1.0/src/dummy
drwxrwxr-x 0/0 0 1970-01-01 01:00 dummy-0.1.0/src/dummy/submodule
-rw-rw-r-- 0/0 30 1970-01-01 01:00 dummy-0.1.0/src/dummy/submodule/impl.py
-rw-rw-r-- 0/0 14 1970-01-01 01:00 dummy-0.1.0/src/dummy/submodule/__init__.py
-rw-rw-r-- 0/0 12 1970-01-01 01:00 dummy-0.1.0/src/dummy/__init__.py
```
No tests since the source distributions don't build valid wheels yet.
As per
https://matklad.github.io/2021/02/27/delete-cargo-integration-tests.html
Before that, there were 91 separate integration tests binary.
(As discussed on Discord — I've done the `uv` crate, there's still a few
more commits coming before this is mergeable, and I want to see how it
performs in CI and locally).