patdiff: new module

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

modules/programs/git.nix

@@ -316,16 +316,6 @@ in
         };
       };
 
-      patdiff = {
-        enable = mkEnableOption "" // {
-          description = ''
-            Whether to enable the {command}`patdiff` differ.
-            See <https://opensource.janestreet.com/patdiff/>
-          '';
-        };
-
-        package = mkPackageOption pkgs "patdiff" { };
-      };
     };
   };
 
@@ -355,8 +345,8 @@ in
                   (config.programs.diff-highlight.enable && config.programs.diff-highlight.enableGitIntegration)
                   (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
-                  cfg.patdiff.enable
                 ];
               in
               lib.count lib.id enabled <= 1;
@@ -654,20 +644,6 @@ in
         }
       )
 
-      (
-        let
-          patdiffPackage = cfg.patdiff.package;
-          patdiffCommand = "${lib.getExe' patdiffPackage "patdiff-git-wrapper"}";
-        in
-        mkIf cfg.patdiff.enable {
-          home.packages = [ patdiffPackage ];
-
-          programs.git.iniContent = {
-            diff.external = patdiffCommand;
-          };
-        }
-      )
-
       (mkIf (cfg.riff.enable && cfg.riff.commandLineOptions != "") {
         home.sessionVariables.RIFF = cfg.riff.commandLineOptions;
       })

modules/programs/patdiff.nix

@@ -0,0 +1,86 @@
+{
+  config,
+  options,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.programs.patdiff;
+
+  inherit (lib)
+    mkEnableOption
+    mkIf
+    mkPackageOption
+    mkOption
+    types
+    ;
+in
+{
+  meta.maintainers = with lib.maintainers; [ khaneliman ];
+
+  imports = [
+    (lib.mkRenamedOptionModule
+      [ "programs" "git" "patdiff" "enable" ]
+      [ "programs" "patdiff" "enable" ]
+    )
+    (lib.mkRenamedOptionModule
+      [ "programs" "git" "patdiff" "package" ]
+      [ "programs" "patdiff" "package" ]
+    )
+  ];
+
+  options.programs.patdiff = {
+    enable = mkEnableOption "" // {
+      description = ''
+        Whether to enable the {command}`patdiff` differ.
+        See <https://opensource.janestreet.com/patdiff/>
+      '';
+    };
+
+    package = mkPackageOption pkgs "patdiff" { };
+
+    enableGitIntegration = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Whether to enable git integration for patdiff.
+
+        When enabled, patdiff will be configured as git's external diff tool.
+      '';
+    };
+  };
+
+  config =
+    let
+      oldOption = lib.attrByPath [ "programs" "git" "patdiff" "enable" ] null options;
+      oldOptionEnabled =
+        oldOption != null && oldOption.isDefined && (builtins.length oldOption.files) > 0;
+    in
+    lib.mkMerge [
+      (mkIf cfg.enable {
+        home.packages = [ cfg.package ];
+
+        # Auto-enable git integration if programs.git.patdiff.enable was set to true
+        programs.patdiff.enableGitIntegration = lib.mkIf oldOptionEnabled (lib.mkOverride 1490 true);
+
+        warnings =
+          lib.optional
+            (cfg.enableGitIntegration && options.programs.patdiff.enableGitIntegration.highestPrio == 1490)
+            "`programs.patdiff.enableGitIntegration` automatic enablement is deprecated. Please explicitly set `programs.patdiff.enableGitIntegration = true`.";
+      })
+
+      (mkIf (cfg.enable && cfg.enableGitIntegration) {
+        programs.git = {
+          enable = lib.mkDefault true;
+          iniContent =
+            let
+              patdiffCommand = "${lib.getExe' cfg.package "patdiff-git-wrapper"}";
+            in
+            {
+              diff.external = patdiffCommand;
+            };
+        };
+      })
+    ];
+}

tests/modules/programs/git/default.nix

@@ -10,5 +10,4 @@
   git-with-hooks = ./git-with-hooks.nix;
   git-with-lfs = ./git-with-lfs.nix;
   git-with-maintenance = ./git-with-maintenance.nix;
-  git-patdiff = ./git-patdiff.nix;
 }

tests/modules/programs/git/git-patdiff-expected.conf

@@ -1,19 +0,0 @@
-[commit]
-	gpgSign = true
-
-[diff]
-	external = "@patdiff@/bin/patdiff-git-wrapper"
-
-[gpg]
-	format = "openpgp"
-
-[gpg "openpgp"]
-	program = "path-to-gpg"
-
-[tag]
-	gpgSign = true
-
-[user]
-	email = "user@example.org"
-	name = "John Doe"
-	signingKey = "00112233445566778899AABBCCDDEEFF"

tests/modules/programs/git/git-patdiff.nix

@@ -1,20 +0,0 @@
-{
-  programs.git = {
-    enable = true;
-    signing = {
-      signer = "path-to-gpg";
-      format = "openpgp";
-      key = "00112233445566778899AABBCCDDEEFF";
-      signByDefault = true;
-    };
-    userEmail = "user@example.org";
-    userName = "John Doe";
-
-    patdiff.enable = true;
-  };
-
-  nmt.script = ''
-    assertFileExists home-files/.config/git/config
-    assertFileContent home-files/.config/git/config ${./git-patdiff-expected.conf}
-  '';
-}