c7ade6844f
This reverts commit eec83d41e3e7d9ad5bc1086198d972d55bab1203. This broke hydra evaluation because with this commit submodule values are allowed to be paths, however the certmgr module uses `either (submodule ...) path` in its type, meaning it already used paths for something else which would now be interpreted as a submodule.
To build the manual, you need Nix installed on your system (no need
for NixOS). To install Nix, follow the instructions at
https://nixos.org/nix/download.html
When you have Nix on your system, in the root directory of the project
(i.e., `nixpkgs`), run:
nix-build nixos/release.nix -A manual.x86_64-linux
When this command successfully finishes, it will tell you where the
manual got generated.