With this change, it's now possible to configure the default search
engine in Firefox with
programs.firefox.profiles.<name>.search.default
and add custom engines with
programs.firefox.profiles.<name>.search.engines.
It's also recommended to enable
programs.firefox.profiles.<name>.search.force = true
since Firefox will replace the symlink for the search configuration on
every launch, but note that you'll loose any existing configuration by
enabling this.
This replaces some derivation outputs by simple strings rather than
full Nix store paths. This removes the need to download the whole
derivation when all we need is a static string.
This makes the
programs.firefox.package
option take a pre-wrapped Firefox package as value if state version is
set to "19.09" or later. This should make the Firefox module work with
a wider range of Firefox packages.