zi switch folding on or off
za toggle current fold open/closed
zc close current fold
zR open all folds
zM close all folds
]m Go to start of next method definition.
]M Go to end of next method definition.
[m Go to start of previous method definition.
[M Go to end of previous method definition.
am "a method", select from "def" until matching "end" keyword.
im "inner method", select contents of "def"/"end" block.
aM "a class", select from "class" until matching "end keyword".
iM "inner class", select contents of "class"/"end" block.