fish: Fix flatpak complaining about XDG_DATA_DIRS

fish/.config/fish/config.fish

@@ -393,3 +393,14 @@ fzf_key_bindings
 
 starship init fish | source
 fnm env | source
+
+# https://github.com/fish-shell/fish-shell/issues/7485#issuecomment-728984689
+# https://wiki.archlinux.org/title/Flatpak#Adding_Flatpak_.desktop_files_to_your_menu
+set -l xdg_data_home $XDG_DATA_HOME ~/.local/share
+set -gx --path XDG_DATA_DIRS $xdg_data_home[1]/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share:/usr/share
+
+for flatpakdir in ~/.local/share/flatpak/exports/bin /var/lib/flatpak/exports/bin
+  if test -d $flatpakdir
+    contains $flatpakdir $PATH; or set -a PATH $flatpakdir
+  end
+end