user-shell.nix battery does not change user shell on macOS

[jacobranson]

There's a couple of issues at play here and I think they are all to do with nix-darwin.

The documentation from nix-darwin reads as follows:

users.users.<name>.shell

The user’s shell. This defaults to null.

When this is set to null, if the user has not been created yet, they will be created with the shell /usr/bin/false to prevent interactive login. If the user already exists, the value is considered managed by macOS and nix-darwin will not change it.

There is this issue regarding users struggling to change the default shell using nix-darwin, which led to this pull request being opened, which would document the fact that both users.knownUsers and users.users.<name>.uid need to be populated for the setting to work.

I would think that the correct place to put this logic would be either in the user-shell battery or the primary-user battery. I don't love the idea of having to hardcode 501 as the uid for my user in my config because it could theoretically change upon a reinstall or a new device being configured differently out of the box.

Happy to discuss more and do some testing if needed. Loving den so far, thank you!