feat(git): use difftastic as diff viewer

home-manager/git.nix

@@ -22,6 +22,12 @@
         rebase.autostash = true;
         rerere.enabled = true;
         worktree.guessRemote = true;
+
+        diff.external = "difft --background light";
+        diff.tool = "difftastic";
+        difftool.prompt = false;
+        difftool.difftastic.cmd = "difft --background light \"$LOCAL\" \"$REMOTE\"";
+        pager.difftool = true;
       };
 
       aliases = {

home-mandlm.nix

@@ -26,6 +26,7 @@
       tree
       light
       element-desktop
+      difftastic
     ];
 
     stateVersion = "22.05";