tex-fmt: add module

tex-fmt is a LaTeX source code formatter written in Rust, and uses
a user configuration file in the .toml format.

modules/modules.nix

@@ -236,6 +236,7 @@ let
     ./programs/tealdeer.nix
     ./programs/terminator.nix
     ./programs/termite.nix
+    ./programs/tex-fmt.nix
     ./programs/texlive.nix
     ./programs/thefuck.nix
     ./programs/thunderbird.nix

modules/programs/tex-fmt.nix

@@ -0,0 +1,40 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.programs.tex-fmt;
+  configPath = "${config.xdg.configHome}/tex-fmt/tex-fmt.toml";
+in {
+  meta.maintainers = [ maintainers.wgunderwood ];
+
+  options = {
+    programs.tex-fmt = {
+      enable = mkEnableOption "tex-fmt";
+      package = mkPackageOption pkgs "tex-fmt" { };
+      options = mkOption {
+        default = { };
+        type = with types; attrsOf (oneOf [ str bool int ]);
+        description = ''
+          List of options to pass to tex-fmt.
+
+          See <https://github.com/WGUNDERWOOD/tex-fmt/blob/master/tex-fmt.toml>
+          for an example configuration.
+        '';
+        example = {
+          usetabs = true;
+          wraplen = 70;
+        };
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    home = mkMerge [
+      { packages = [ cfg.package ]; }
+      (mkIf (cfg.options != [ ]) {
+        file."${configPath}".text = lib.concatLines cfg.options;
+      })
+    ];
+  };
+}