WIP: add jujutsu (w/ Delta)

modules/home/delta/default.nix

@@ -11,9 +11,24 @@ in
     git = {
       enable = my.mkDisableOption "git integration";
     };
+
+    jujutsu = {
+      enable = my.mkDisableOption "jujutsu integration";
+    };
   };
 
   config = lib.mkIf cfg.enable {
+    assertions = [
+      {
+        # For its configuration
+        assertion = cfg.jujutsu.enable -> cfg.git.enable;
+        message = ''
+          `config.my.home.delta.jujutsu` relies on `config.my.home.delta.git`
+          being enabled.
+        '';
+      }
+    ];
+
     home.packages = [ cfg.package ];
 
     programs.git = lib.mkIf cfg.git.enable {
@@ -46,5 +61,25 @@ in
         };
       };
     };
+
+    programs.jujutsu = lib.mkIf cfg.jujutsu.enable {
+      settings = {
+        merge-tools = {
+          delta = {
+            # Errors are signaled with exit codes greater or equal to 2
+            diff-expected-exit-codes = [ 0 1 ];
+          };
+        };
+
+        ui = {
+          diff = {
+            # Delta expects a `git diff` input
+            format = "git";
+          };
+
+          pager = "delta";
+        };
+      };
+    };
   };
 }