`man 1 info` says:
The first non-option argument, if present, is the menu entry to
start from; it is searched for in all `dir' files along INFOPATH.
If it is not present, info merges all `dir' files and shows the
result. Any remaining arguments are treated as the names of menu
items relative to the initial node visited.
Which means that this does what previous programs/info did and #8519
(on-the-fly infodir generation for Emacs) wanted to do, but for both
programs.
This improves error messages when a set or a list is used where a path
was expected. For an example, if you used a package set (as opposed to a
single package) in systemPackages before this commit, the error was:
```
cannot coerce a list to a string, at "/home/nixpkgs/lib/types.nix":103:37
```
Now, the error message reads:
```
The option value `environment.systemPackages' in `/etc/nixos/configuration.nix' is not a list of paths.
```
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
