Can't install/remove source packages from a repository: Argument... matches only source packages

[ppisar]

It was reported in Fedora that source packages cannot be installed from a repository:

# dnf --repoid rawhide-source install dontpanic.src
Updating and loading repositories:
Repositories loaded.
Failed to resolve the transaction:
Argument 'dontpanic.src' matches only source packages.

They can be installed from a local package:

# dnf5 install ~test/rpmbuild/SRPMS/foo-0-0.fc42.src.rpm 
[...]
Package                         Arch      Version                          Repository              Size
Installing:
 foo                            src       0-0.fc42                         @commandline       399.0   B

Transaction Summary:
 Installing:        1 packages
[...]
[3/3] Installing foo-0:0-0.fc42.src                            100% |   4.6 KiB/s | 644.0   B |  00m00s
Warning: skipped PGP checks for 1 package from repository: @commandline
Complete!

But cannot be uninstalled regardless their provenance:

# rpm -q foo
foo-0-0.fc42.src
root@fedora-42:~ # dnf5 remove foo
Argument 'foo' matches only source packages.

Nothing to do.

The error comes from GoalProblem Transaction::Impl::report_not_found() which unconditionally excludes all source packages:

    query.filter_arch(std::vector<std::string>{"src", "nosrc"}, sack::QueryCmp::NEQ);
    if (query.empty()) {
        add_resolve_log(
            action,
            GoalProblem::ONLY_SRC,
            settings,
            libdnf5::transaction::TransactionItemType::PACKAGE,
            pkg_spec,
            {},
            log_level);
        return GoalProblem::ONLY_SRC;
    }       

That error-reporting method is called from GoalProblem Goal::Impl::add_remove_to_goal() and similar GoalProblem Goal::Impl methods.

It seems that DNF5 forgot to support operations on source packages as a simplification of discriminating among architectures.