I built my $XDG_CONFIG_HOME/gopass/config using Nix, but I had to do some ugly fiddling, to make it work:

source = (pkgs.formats.ini { }).generate "gopass.config" {
    …
    "mounts" = {
    "\tpath " = " ${stores}/mcnesium";
    "\tremote " = " ${remote}:passwords/mcnesium.git";
    };

The \t and the spaces around the = were necessary to make the INI format look like this:

[mounts]
    path = /home/mcn/.local/share/gopass/stores/mcnesium
    remote = git@git.qwertz.de:passwords/mcnesium.git

and not like it would generate it without them:

[mounts]
path=/home/mcn/.local/share/gopass/stores/mcnesium
remote=git@git.qwertz.de:passwords/mcnesium.git

With the latter, gopass mounts would simply return that it won't find any configured mounts.

The Nix community argues, gopass would be too picky with the file format, as INI itself would not rely on those tabs and spaces.