pet: add module

Adds a pet module without sync support as it makes no sense when
configuration is managed with Home Manager and the config would be
unwritable for pet anyway.

PR #1045

modules/programs/pet.nix

@@ -0,0 +1,88 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.programs.pet;
+
+  format = pkgs.formats.toml { };
+
+  snippetType = types.submodule {
+    options = {
+      description = mkOption {
+        type = types.str;
+        default = "";
+        example = "Count the number of commits in the current branch";
+        description = ''
+          Description of the snippet.
+        '';
+      };
+
+      command = mkOption {
+        type = types.str;
+        default = "";
+        example = "git rev-list --count HEAD";
+        description = ''
+          The command.
+        '';
+      };
+
+      output = mkOption {
+        type = types.str;
+        default = "";
+        example = "473";
+        description = ''
+          Example output of the command.
+        '';
+      };
+    };
+  };
+
+in {
+  options.programs.pet = {
+    enable = mkEnableOption "pet";
+
+    settings = mkOption {
+      type = format.type;
+      default = { };
+      description = ''
+        Settings written to <filename>config.toml</filename>. See the pet
+        documentation for details.
+      '';
+    };
+
+    selectcmdPackage = mkOption {
+      type = types.package;
+      default = pkgs.fzf;
+      defaultText = literalExample "pkgs.fzf";
+      description = ''
+        The package needed for the <varname>settings.selectcmd</varname>.
+      '';
+    };
+
+    snippets = mkOption {
+      type = types.listOf snippetType;
+      default = [ ];
+      description = ''
+        The snippets.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    programs.pet.settings = {
+      selectcmd = mkDefault "fzf";
+      snippetfile = config.xdg.configHome + "/pet/snippet.toml";
+    };
+
+    home.packages = [ pkgs.pet cfg.selectcmdPackage ];
+
+    xdg.configFile = {
+      "pet/config.toml".source =
+        format.generate "config.toml" { General = cfg.settings; };
+      "pet/snippet.toml".source =
+        format.generate "snippet.toml" { snippets = cfg.snippets; };
+    };
+  };
+}