Using the anaphoric macros from the dash library allows the banner
code to be smaller and I feel more readable. Yes, I could have run the
`ls` command into another buffer and copied it, I have bigger plans
for displaying my directory listing.
My attempt at making a gnarly banner function more readable by
creating lexical functions with `cl-flet` to pass to `mapconcat` was
thwarted! Who would have thunk that `mapconcat' couldn't access a
symbol reference to a function created by `cl-flet*'!?
Whenever I open a shell, even if I know where and why I'm there, I
always type `ls`, so in this case, I made the eshell banner display
a listing of all of the files.
