map {lhs} <Plug>(operator-agg)
Executing the {lhs} command followed by a motion like iW will ag the current directory for the text selected by the motion.
map {lhs} <Plug>(operator-ag)
This variant leaves vim in command-line mode, allowing you to specify a search path or additional ag parameters.
g:operator_ag_cmd = 'Ag!'
The command to be executed.
g:operator_ag_escape = 1
Whether or not the selected text should be shellescaped.
This is necessary for :Ag, as its arguments are being passed to the shell as-is.
When using a different approach, e.g. via Unite, set this to 0.