unstable order in generated usage

[warpfork]

The order of flags described in the generated usage appears to be random. (I guess it is effectively the iteration order of the bash associative maps.)

For example, the current output of one of the tutorial scripts is:

6-properties [ --option8 ] [ --option3 ] --option1 [ --option6 ] [ --option7 ] \
	[ --option4 ] [ --option5 ] [ --help ]

      --option8   A 8th option
		 Requires: --option2 --option3
      --option3   A 3rd option.
      --option1   A mandatory option.
      --option6   A 6th option.
		 Same as: --option1 --option2 --option3
      --option7   A 7th option
		 Same as: --option6
      --option4   A 4th option.
      --option5   A 5th option.
 -h | --help      Show this help message

This is moderately confusing. Either sorted, or persisting the order in which they are defined, would be preferable.