mirror: --exclude-module/--exclude-package ignore the @version part

Summary

--exclude-module <name>@<version> (and --exclude-package <name>@<version>) ignore the @version part. The documented format is module-name[@version], which implies version-level exclusion, but the whole module/package is excluded regardless of the version supplied.

Details

In blacklist mode Filter.Match matches by name only:

• internal/mirror/modules/filter.go — Match checks f.modules[mod.Name]; the parsed version constraint is stored but never consulted.

The @version is still parsed at flag-processing time (so it must be a valid semver/constraint, otherwise the command errors), but it has no effect on what is excluded.

Packages reuse modules.Filter, so --exclude-package behaves the same way.

Impact

Silent over-exclusion. A user running --exclude-module foo@1.2.0 expecting to drop a single version actually drops all versions of foo, with no warning.

Expected

Either honor the version constraint in blacklist mode, or reject/document --exclude-module / --exclude-package as name-only.

As of main (62132d6a).

Start in internal/mirror/modules/filter.go and trace Filter.Match from the mirror command's exclude-module and exclude-package flag handling. Check how parsed version constraints are stored and whether blacklist matching uses them. Done means version-specific exclusions behave as documented, or the name-only behavior is explicitly rejected or documented, with coverage for both module and package flags.