How to build a package in a local clone of nixpkgs

For example, if you need to update hashes manually, or test package in the shell

First, clone nixpkgs:

git clone https://github.com/NixOS/nixpkgs

Then, run from nixpkgs folder:

nix repl
# or, if some env variables is needed (e.g. NIXPKGS_ALLOW_INSECURE):
nix repl --impure

And then in the repl:

• Load nixpkgs: :l .
• Reload nixpkgs after editing packages: :r
• Build a package: :b pkgs.your-package
• Build a package and open shell with it: :u pkgs.your-package