Git, *sh: make less more better

Bring shell and Git less variables into sync, and add some new hotness.

Git gets a verbose prompt (M).

The shells get immediate exit if output fits on one screen (F) and
chopped long-lines (S).

Both Git and the shells get "smart" case-insensitive search (i).

Signed-off-by: Greg Hurrell <greg@hurrell.net>