tv alacritty: mkdir and cp only when needed

tv/5pkgs/simple/alacritty-tv.nix

@@ -51,17 +51,7 @@ let
     scrolling.multiplier = 8;
   };
   config-file = pkgs.writeJSON "alacritty-tv.json" config;
-in
-
-pkgs.symlinkJoin {
-  name = "alacritty-tv";
-  paths = [
-    (pkgs.writeDashBin "alacritty" ''
-      # usage:
-      #   alacritty [--singleton] [ARGS...]
-
-      set -efu
-
+  profile = pkgs.writeText "alacritty-tv.profile" /* sh */ ''
     # Use home so Alacritty can find the configuration without arguments.
     # HOME will be reset once in Alacritty.
     HOME=$TMPDIR/Alacritty
@@ -74,15 +64,28 @@ pkgs.symlinkJoin {
       echo ${config-file} > "$HOME"/ref
       ${pkgs.coreutils}/bin/cp ${config-file} "$HOME"/.alacritty.yml
     fi
+  '';
+in
+
+pkgs.symlinkJoin {
+  name = "alacritty-tv";
+  paths = [
+    (pkgs.writeDashBin "alacritty" ''
+      # usage:
+      #   alacritty [--singleton] [ARGS...]
+
+      set -efu
 
       case ''${1-} in
         --singleton)
           shift
           if ! ${pkgs.alacritty}/bin/alacritty msg create-window "$@"; then
+            . ${profile}
             ${pkgs.alacritty}/bin/alacritty "$@" &
           fi
           ;;
         *)
+          . ${profile}
           exec ${pkgs.alacritty}/bin/alacritty "$@"
           ;;
       esac