Copy over pep440-rs crate (#30)

This PR copies over the `pep440-rs` crate at commit
`a8303b01ffef6fccfdce562a887f6b110d482ef3` with no modifications.

It won't pass CI, but modifications will intentionally be confined to
later PRs.

crates/pep440-rs/python/Readme.md

@@ -0,0 +1,42 @@
+# PEP440 in rust
+
+A library for python version numbers and specifiers, implementing
+[PEP 440](https://peps.python.org/pep-0440)
+
+```shell
+pip install pep440_rs
+```
+
+```python
+from pep440_rs import Version, VersionSpecifier
+
+assert Version("1.1a1").any_prerelease()
+assert Version("1.1.dev2").any_prerelease()
+assert not Version("1.1").any_prerelease()
+assert VersionSpecifier(">=1.0").contains(Version("1.1a1"))
+assert not VersionSpecifier(">=1.1").contains(Version("1.1a1"))
+assert Version("2.0") in VersionSpecifier("==2")
+```
+
+Unlike [pypa/packaging](https://github.com/pypa/packaging), this library always matches preleases. To only match final releases, filter with `.any_prelease()` beforehand.
+
+PEP 440 has a lot of unintuitive features, including:
+
+* An epoch that you can prefix the version which, e.g. `1!1.2.3`. Lower epoch always means lower
+  version (`1.0 <=2!0.1`)
+* post versions, which can be attached to both stable releases and prereleases
+* dev versions, which can be attached to sbpth table releases and prereleases. When attached to a
+  prerelease the dev version is ordered just below the normal prerelease, however when attached
+  to a stable version, the dev version is sorted before a prereleases
+* prerelease handling is a mess: "Pre-releases of any kind, including developmental releases,
+  are implicitly excluded from all version specifiers, unless they are already present on the
+  system, explicitly requested by the user, or if the only available version that satisfies
+  the version specifier is a pre-release.". This means that we can't say whether a specifier
+  matches without also looking at the environment
+* prelease vs. prerelease incl. dev is fuzzy
+* local versions on top of all the others, which are added with a + and have implicitly typed
+  string and number segments
+* no semver-caret (`^`), but a pseudo-semver tilde (`~=`)
+* ordering contradicts matching: We have e.g. `1.0+local > 1.0` when sorting,
+  but `==1.0` matches `1.0+local`. While the ordering of versions itself is a total order
+  the version matching needs to catch all sorts of special cases

crates/pep440-rs/python/pep440_rs/__init__.py

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+"""
+A PEP440 reimplementation in rust
+
+```python
+from pep440_rs import Version, VersionSpecifier
+
+
+assert Version("1.1a1").any_prerelease()
+assert Version("1.1.dev2").any_prerelease()
+assert not Version("1.1").any_prerelease()
+assert VersionSpecifier(">=1.0").contains(Version("1.1a1"))
+assert not VersionSpecifier(">=1.1").contains(Version("1.1a1"))
+assert Version("2.0") in VersionSpecifier("==2")
+```
+
+"""
+
+from ._pep440_rs import *
+
+__doc__ = _pep440_rs.__doc__
+if hasattr(_pep440_rs, "__all__"):
+    __all__ = _pep440_rs.__all__

crates/pep440-rs/python/pep440_rs/__init__.pyi

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+# Generated by `stubgen -p pep440_rs`
+from typing import Any, ClassVar
+
+
+class Version:
+    dev: Any
+    epoch: Any
+    post: Any
+    pre: Any
+    release: Any
+    major: Any
+    minor: Any
+    micro: Any
+
+    @classmethod
+    def __init__(cls, *args, **kwargs) -> None: ...
+    def any_prerelease(self, *args, **kwargs) -> Any: ...
+    def parse_star(self, *args, **kwargs) -> Any: ...
+    def __eq__(self, other) -> Any: ...
+    def __ge__(self, other) -> Any: ...
+    def __gt__(self, other) -> Any: ...
+    def __hash__(self) -> Any: ...
+    def __le__(self, other) -> Any: ...
+    def __lt__(self, other) -> Any: ...
+    def __ne__(self, other) -> Any: ...
+
+
+class VersionSpecifier:
+    __hash__: ClassVar[None] = ...
+
+    @classmethod
+    def __init__(cls, *args, **kwargs) -> None: ...
+    def contains(self, *args, **kwargs) -> Any: ...
+    def __contains__(self, other) -> Any: ...
+    def __eq__(self, other) -> Any: ...
+    def __ge__(self, other) -> Any: ...
+    def __gt__(self, other) -> Any: ...
+    def __le__(self, other) -> Any: ...
+    def __lt__(self, other) -> Any: ...
+    def __ne__(self, other) -> Any: ...