Channel names with `.` or `-` don't work with nix-env -iA attribute paths or don't work with nix-channel --remove

[CMCDragonkai]

When you create a channel with . or - in its name like: nix-channel --add https://nixos.org/channels/nixos-17.03-small nixos-17.03-small. And then you try to use it with an attribute path like nix-env -iA 'nixos-17.03-small.hello, nix-env complains that it cannot find the attribute path. But if you instead give it a name like A, then it will work!

This is happening on 1.11.15.

[CMCDragonkai]

This error also affects deletion of channels like nix-channel --remove nixos-17.03-small will just not work.

But removal problem is caused by the - character as well.

[CMCDragonkai]

This error is the same error as described here: #1067

[CMCDragonkai]

To resolve this, channel names should not be allowed to have ., while nix-channel needs to be fixed to allow - in their names.