Pill 15 makes a promise for pill 16 which is not kept

[jkozak]

Pill 15 contains:

You may wonder: then I can also specify a different nixpkgs path to, 
e.g., a git checkout of nixpkgs? Yes, you can and I encourage doing
that. We'll talk about this in the next pill.

There is no discussion of this that I can find in pill 16.

[fricklerhandwerk]

@jkozak Thanks for pointing that out. No one really maintains these pills these days, even though many use it for learning about the inner workings of Nixpkgs. Would you mind making a PR to fix this: either remove that phrase or add a section that fulfills the promise?

[jkozak]

I could probably hack something together to do this, but I'm not sure what the approved way is, which is why I was please to see this claim in pill 15.
While I could remove it altogether, it would be good to have an official HOWTO somewhere.

[fricklerhandwerk]

This is done with the -I option. The manual is currently in an unfortunate state about that. It is documented, but only for the new CLI commands such as nix build, which don't have anchors to link to directly.

The instructions on nix.dev are currently as official as it gets.