> If the performance still looks okay to you, I have no objections. Just
> remove that last argument, and it's good to install.

I'd say that Damien can try it out and report if it works well enough.
I worry that the files returned by `directory-files-recursively' might
slow down the function considerably.  Perhaps it might be better to
write a little function just for project.el to only generate a list of
directories.