Add -FX flags to the pager so that less doesn't clear the screen for a short diff and doesn't wait for the user to press Q to return to the shell

-F makes less return immediately if the content fits on the screen. Without this you need to press Q to get back to your shell even if the diff was only a few lines long
-X prevent less from clearing the screen at the beginning. Which is undesirable if the content fits on one screen and unnecessary if the content is longer than a screen.

And the -R flag (not added by this PR) displays colors correctly instead of outputting as ASCII representation of the control chars

Author: arthurdarcet

readme.md

@@ -21,8 +21,8 @@ git diff --color | diff-so-fancy
 
 **But**, you'll probably want to fancify all your diffs. Run this so `git diff` and `git show` will use it:
 ```shell
-git config --global pager.diff "diff-so-fancy | less --tabs=1,5 -R"
-git config --global pager.show "diff-so-fancy | less --tabs=1,5 -R"
+git config --global pager.diff "diff-so-fancy | less --tabs=1,5 -RFX"
+git config --global pager.show "diff-so-fancy | less --tabs=1,5 -RFX"
 ```
 
 Or, create a git alias  in your `~/.gitconfig` for shorthand fanciness: