nix build handles flake references differently depending on if they explicitly say "path:"

[colemickens]

Describe the bug

see: NixOS/nixpkgs#144811

It seems that nix build FOO does different things when FOO is ~/some/path vs path:~/some/path.

This might also explain another issue I found long ago, with nixos-rebuild: NixOS/nixpkgs#101648

This bug strikes me as odd, why is the path parsing code not being handled the same at this point when it's been guessed or specified as a path?

[thufschmitt]

I don’t know whether that’s the cause of your issues, but nix build /some/path will indeed resolve to git+file:///some/path if /some/path is a git repository, or path:/some/path otherwise. Which I think makes perfect sense, because people (well, me at least) will expect nix build . to work regardless of whether I’m in a git repo or not, and to play with git if I’m in a git repo.
And having a way to explicitly specify path:FOO is also very handy for the 1% cases where I need to force the use of a plain path even if the path is a git repository.