Minibuffer can be edited similarly to Insert state, and you
can switch between Insert/Replace/Vi states at will. Some users
prefer plain Emacs feel in the minibuffer. To this end, set
viper-vi-style-in-minibuffer to nil.
C-v
Deprive the next char of its special meaning
(quoting).
C-h
One char back.
C-w
One word back.
C-u
Back to the begin of the change on the current line.