(fish) pretty fish title and command not found function

.config/fish/functions/fish_command_not_found.fish

@@ -0,0 +1,4 @@
+function fish_command_not_found
+    echo Did not find command $argv[1]
+    pkgfile -s $argv[1]
+end

.config/fish/functions/fish_title.fish

@@ -0,0 +1,7 @@
+function fish_title
+    if [ $_ = 'fish' ]
+        echo " " (prompt_pwd)
+    else
+        echo $_
+    end
+end