home-manager: Use path: URI type for flake default

[dongcarl]

Nix interprets a path-like URI as a git repository if any of the path's parents is a git repository. Since home-manager uses a default flake URI of ~/.config/nixpkgs/flake.nix, if you have a git repository as your home directory and a '*' .gitignore it leads to the following problems:

    evaluating derivation 'git+file:///Users/dongcarl?dir=.config%2fnixpkgs#homeConfigurations."dongcarl".activationPackage'
    The following paths are ignored by one of your .gitignore files:
    .config

This is solved by explicitly specifying the `path:` URI type prefix for the default flake URI argument.

I hope that this fix gets backported to release branches.

[ncfavier]

Not sure I understand. The directory with your flake.nix in it should be a git repository anyway, otherwise Nix commands won't work?

if you have a git repository as your home directory

I don't think Home Manager should support this use case, since it's kind of meant to avoid it...

[dongcarl]

Not sure I understand. The directory with your flake.nix in it should be a git repository anyway, otherwise Nix commands won't work?

Flake URIs seem to support mercurial, tarballs, paths, plain files, etc. So it doesn't need to be a git repository, in home-manager's default case, we only know that the flake.nix file exists, but not if it's in a mercurial, git, or just a plain path, so I think a sane default is path: since that's the common denominator.

However, if home-manager wants to be opinionated in favor of git, an alternative solution is to at least print a more helpful message if it's detected that $HOME/.config/nixpkgs is not a git repository and prompt the user to not rely on the default and specify their own flake URI.

[rycee]

Seems reasonable. Will this cause any difference in behavior if you have ~/.config/nixpkgs as a Git repository?

[dongcarl]

Seems reasonable. Will this cause any difference in behavior if you have ~/.config/nixpkgs as a Git repository?

Just tried, no difference in behavior!

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