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/test/test_python.py

@@ -0,0 +1,48 @@
+"""
+This is implementation has some very rudimentary python bindings
+"""
+from pep440_rs import Version, VersionSpecifier, Operator, VersionSpecifiers
+
+
+def test_pep440():
+    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("1.1") >= Version("1.1a1")
+    assert Version("2.0") in VersionSpecifier("==2")
+    assert Version("2.1").major == 2
+    assert Version("2.1").minor == 1
+    assert Version("2.1").micro == 0
+
+
+def test_version_specifier():
+    assert VersionSpecifier(">=1.1").version == Version("1.1")
+    assert VersionSpecifier(">=1.1").operator == Operator.GreaterThanEqual
+    assert str(VersionSpecifier(">=1.1").operator) == ">="
+    # Note: This removes the star
+    assert VersionSpecifier("==1.1.*").version == Version("1.1")
+    assert str(VersionSpecifier("==1.1.*").operator) == "=="
+    assert {
+        VersionSpecifier("==1.1.*"),
+        VersionSpecifier("==1.1"),
+        VersionSpecifier("==1.1"),
+    } == {VersionSpecifier("==1.1.*"), VersionSpecifier("==1.1")}
+
+
+def test_version_specifiers():
+    assert str(VersionSpecifiers(">=1.1, <2.0")) == ">=1.1, <2.0"
+    assert list(VersionSpecifiers(">=1.1, <2.0")) == [
+        VersionSpecifier(">=1.1"),
+        VersionSpecifier("<2.0"),
+    ]
+
+
+def test_normalization():
+    assert str(Version("1.19-alpha.1")) == "1.19a1"
+    assert str(VersionSpecifier(" >=1.19-alpha.1 ")) == ">=1.19a1"
+    assert repr(Version("1.19-alpha.1")) == '<Version("1.19a1")>'
+    assert (
+        repr(VersionSpecifier(" >=1.19-alpha.1 ")) == '<VersionSpecifier(">=1.19a1")>'
+    )