refactor: put behind a compare subcommand

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

Author: henryiii

src/packaging/tags.py

@@ -114,7 +114,10 @@ def __str__(self) -> str:
         return f"{self._interpreter}-{self._abi}-{self._platform}"
 
     def __repr__(self) -> str:
-        return f"<{self} @ {id(self)}>"
+        return (
+            f"{self.__class__.__name__}"
+            f"({self._interpreter!r}, {self._abi!r}, {self._platform!r})"
+        )
 
     def __setstate__(self, state: tuple[None, dict[str, Any]]) -> None:
         # The cached _hash is wrong when unpickling.

src/packaging/version.py

@@ -930,6 +930,7 @@ def _cmpkey(
 
     return epoch, _release, _pre, _post, _dev, _local
 
+
 if __name__ == "__main__":
     import argparse
     import operator
@@ -949,18 +950,24 @@ def _cmpkey(
         ">": operator.gt,
     }
 
-    # Argument parsing
-    parser = argparse.ArgumentParser(description="Compare two semantic versions. Return code is 0 or 1.")
-    parser.add_argument("version1", type=Version, help="First version to compare")
-    parser.add_argument(
+    parser = argparse.ArgumentParser(description="Version utilities")
+    subparsers = parser.add_subparsers(dest="command", required=True)
+
+    compare = subparsers.add_parser(
+        "compare",
+        help="Compare two semantic versions.",
+        description="Compare two semantic versions. Return code is 0 or 1.",
+    )
+    compare.add_argument("version1", type=Version, help="First version to compare")
+    compare.add_argument(
         "operator",
-        type=str,
         choices=operations.keys(),
         help="Comparison operator",
     )
-    parser.add_argument("version2", type=Version, help="Second version to compare")
-    args = parser.parse_args()
+    compare.add_argument("version2", type=Version, help="Second version to compare")
 
-    result = operations[args.operator](args.version1, args.version2)
-    raise SystemExit(not result)
+    args = parser.parse_args()
 
+    if args.command == "compare":
+        result = operations[args.operator](args.version1, args.version2)
+        raise SystemExit(not result)