cc @astsmtl

May be users should use something like

  nixpkgs.overlays = [(self: super: {
    terminus_font = super.terminus_font.overrideAttrs (_: {
      patchPhase = super.terminus_font.patchPhase + ''
        patch -p1 -i alt/ge2.diff
        patch -p1 -i alt/ij1.diff
        patch -p1 -i alt/ll2.diff
        patch -p1 -i alt/td1.diff
      '';
    });
  })];

and options for Terminus font not needed?

Not needed indeed. Just use overlays.

Just in case someone lands here when looking for these options, I'm posting what actually works for me on nixpkgs-unstable today. The way patches are managed has changed, that package doesn't use patchPhase, and it's now:

self: super:
{

  terminus_font = super.terminus_font.overrideAttrs (_: {
      patches = [
        "alt/ll2.diff"
	"alt/td1.diff"
      ];
    });
}

It's enough to put that into ~/.config/nixpkgs/overlays/extra-packages/default.nix.

I think this demonstrates quite nicely that there's some churn in these options, so I think adding per-package options is a cleaner option here. Too bad that even these options are apparently totally undocumented...

Note that the override in the comment above is subtly incorrect — it replaces the value of patches completely, but the current version of the terminus_font package actually has a patch inside, and that patch gets removed by the override.

The correct override should use (old.patches or []) to make sure that any Nixpkgs-provided patches are still applied:

self: super:
{
  terminus_font = super.terminus_font.overrideAttrs (old: {
      patches = (old.patches or []) ++ [
        "alt/ll2.diff"
	"alt/td1.diff"
      ];
    });
}