Why less -F option does not work with -S option

Question

While trying to improve output from hg diff, I noticed that less’s -F option does not work with its -S option. Why is that happening and how can I achieve the desired effect?

Here is an extract from man:

   -F or --quit-if-one-screen
      Causes less to automatically exit if the entire file can be dis-
      played on the first screen.

   -S or --chop-long-lines
      Causes  lines  longer than the screen width to be chopped rather
      than folded.  That is, the portion of a long line that does  not
      fit  in  the  screen width is not shown.  The default is to fold
      long lines; that is, display the remainder on the next line.

Tested on less 444 and less 436.

Explanation

I was mistaken in thinking that -S will cut excess bytes. Content goes to the right of the screen.

To achieve what I wanted I could just use (...) | cut -b -80 | less -FSX.

Answer 1

Works for me; less -FS exits immediately if the input can be printed on one screen without folding lines, and acts normally if scrolling (either to the right or down) is needed.