emacs goodie: auto-wrap a comment block

I always forget this emacs trick: M-q  auto-wraps the current text block to the fill column (default is usually column 70).  This is wondrous for long comments:

“”“Sometimes I like to write a nice long block of text explaining what a function does.  You can wrap it manually, but then it gets all screwy when you need to add something to the middle!”“”

M-x set-fill-column 20
M-q

“”“Sometimes I like
to write a nice long
block of text
explaining what a
function does.  You
can wrap it
manually, but then
it gets all screwy
when you need to add
something to the
middle!”“”