riff: new module

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

modules/programs/git.nix

@@ -293,29 +293,6 @@ in
         };
       };
 
-      riff = {
-        enable = mkEnableOption "" // {
-          description = ''
-            Enable the <command>riff</command> diff highlighter.
-            See <link xlink:href="https://github.com/walles/riff" />.
-          '';
-        };
-
-        package = mkPackageOption pkgs "riffdiff" { };
-
-        commandLineOptions = mkOption {
-          type = types.listOf types.str;
-          default = [ ];
-          example = literalExpression ''[ "--no-adds-only-special" ]'';
-          apply = lib.concatStringsSep " ";
-          description = ''
-            Command line arguments to include in the <command>RIFF</command> environment variable.
-
-            Run <command>riff --help</command> for a full list of options
-          '';
-        };
-      };
-
     };
   };
 
@@ -346,7 +323,7 @@ in
                   (config.programs.diff-so-fancy.enable && config.programs.diff-so-fancy.enableGitIntegration)
                   (config.programs.difftastic.enable && config.programs.difftastic.git.enable)
                   (config.programs.patdiff.enable && config.programs.patdiff.enableGitIntegration)
-                  cfg.riff.enable
+                  (config.programs.riff.enable && config.programs.riff.enableGitIntegration)
                 ];
               in
               lib.count lib.id enabled <= 1;
@@ -624,29 +601,6 @@ in
           };
       })
 
-      (
-        let
-          riffExe = baseNameOf (lib.getExe cfg.riff.package);
-        in
-        mkIf cfg.riff.enable {
-          home.packages = [ cfg.riff.package ];
-
-          # https://github.com/walles/riff/blob/b17e6f17ce807c8652bc59cd46758661d23ce358/README.md#usage
-          programs.git.iniContent = {
-            pager = {
-              diff = riffExe;
-              log = riffExe;
-              show = riffExe;
-            };
-
-            interactive.diffFilter = "${riffExe} --color=on";
-          };
-        }
-      )
-
-      (mkIf (cfg.riff.enable && cfg.riff.commandLineOptions != "") {
-        home.sessionVariables.RIFF = cfg.riff.commandLineOptions;
-      })
     ]
   );
 }

modules/programs/riff.nix

@@ -0,0 +1,107 @@
+{
+  config,
+  options,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.programs.riff;
+
+  inherit (lib)
+    literalExpression
+    mkEnableOption
+    mkIf
+    mkOption
+    mkPackageOption
+    types
+    ;
+in
+{
+  meta.maintainers = with lib.maintainers; [ khaneliman ];
+
+  imports = [
+    (lib.mkRenamedOptionModule [ "programs" "git" "riff" "enable" ] [ "programs" "riff" "enable" ])
+    (lib.mkRenamedOptionModule [ "programs" "git" "riff" "package" ] [ "programs" "riff" "package" ])
+    (lib.mkRenamedOptionModule
+      [ "programs" "git" "riff" "commandLineOptions" ]
+      [ "programs" "riff" "commandLineOptions" ]
+    )
+  ];
+
+  options.programs.riff = {
+    enable = mkEnableOption "" // {
+      description = ''
+        Enable the <command>riff</command> diff highlighter.
+        See <link xlink:href="https://github.com/walles/riff" />.
+      '';
+    };
+
+    package = mkPackageOption pkgs "riffdiff" { };
+
+    commandLineOptions = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      example = literalExpression ''[ "--no-adds-only-special" ]'';
+      apply = lib.concatStringsSep " ";
+      description = ''
+        Command line arguments to include in the <command>RIFF</command> environment variable.
+
+        Run <command>riff --help</command> for a full list of options
+      '';
+    };
+
+    enableGitIntegration = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Whether to enable git integration for riff.
+
+        When enabled, riff will be configured as git's pager for diff, log, and show commands.
+      '';
+    };
+  };
+
+  config =
+    let
+      oldOption = lib.attrByPath [ "programs" "git" "riff" "enable" ] null options;
+      oldOptionEnabled =
+        oldOption != null && oldOption.isDefined && (builtins.length oldOption.files) > 0;
+    in
+    lib.mkMerge [
+      (mkIf cfg.enable {
+        home.packages = [ cfg.package ];
+
+        home.sessionVariables = mkIf (cfg.commandLineOptions != "") {
+          RIFF = cfg.commandLineOptions;
+        };
+
+        # Auto-enable git integration if programs.git.riff.enable was set to true
+        programs.riff.enableGitIntegration = lib.mkIf oldOptionEnabled (lib.mkOverride 1490 true);
+
+        warnings =
+          lib.optional
+            (cfg.enableGitIntegration && options.programs.riff.enableGitIntegration.highestPrio == 1490)
+            "`programs.riff.enableGitIntegration` automatic enablement is deprecated. Please explicitly set `programs.riff.enableGitIntegration = true`.";
+      })
+
+      (mkIf (cfg.enable && cfg.enableGitIntegration) {
+        programs.git = {
+          enable = lib.mkDefault true;
+          iniContent =
+            let
+              riffExe = baseNameOf (lib.getExe cfg.package);
+            in
+            {
+              pager = {
+                diff = riffExe;
+                log = riffExe;
+                show = riffExe;
+              };
+
+              interactive.diffFilter = "${riffExe} --color=on";
+            };
+        };
+      })
+    ];
+}