make the default fish_prompt an autoloaded function

closes 89luca89#1671

Author: capfredf

distrobox-init

@@ -2151,10 +2151,13 @@ if status --is-interactive
 		passwd && rm -f /var/tmp/.\$USER.passwd.initialize
 		trap - INT
 	end
-	function fish_prompt
-		set current_dir (basename (pwd))
-		echo "📦[\$USER@\$CONTAINER_ID \$current_dir]> "
-	end
+end
+EOF
+	mkdir -p /etc/fish/functions
+	cat << EOF > /etc/fish/functions/fish_prompt.fish
+function fish_prompt
+	set current_dir (basename (pwd))
+	echo "📦[\$USER@\$CONTAINER_ID \$current_dir]> "
 end
 EOF
 fi