[xmonad] XPrompt.Shell feature requests

There are a couple things that annoy me about XPrompt.Shell: 1. When tab-completing a directory name, a trailing slash is not automatically appended. Thus an additional keystroke is required, unlike any other tab completion system I’m familiar with (mostly those in bash and Vim). 2. Filenames in the pop-up tab-completion list are escaped. This makes the names harder to read. Could the unescaped filenames appear in the list and then be escaped after tab is pressed as the string is copied into the prompt line? I looked at the source, but only got as far as finding that the completion is done via bash’s compgen builtin. I coudn’t find in bash’s man page how to add slashes to the output of compgen.