Variable: temp-buffer-max-height

Maximum height of a window displaying a temporary buffer.
This is effective only when Temp Buffer Resize mode is enabled.
The value is the maximum height (in lines) which
`resize-temp-buffer-window' will give to a window displaying a
temporary buffer. It can also be a function to be called to
choose the height for such a buffer. It gets one argument, the
buffer, and should return a positive integer. At the time the
function is called, the window to be resized is selected.