Change option name and add command-line help#500

frank-at-adacore wants to merge 8 commits intomasterAdaCore/training_material:masterfrom

slides/214-make-fix_prelude-actually-fix-the-prelude-when-run-from-the-command-lineAdaCore/training_material:slides/214-make-fix_prelude-actually-fix-the-prelude-when-run-from-the-command-lineCopy head branch name to clipboard