Understanding "help" command description syntax - explanation needed

[Chris Angelico]

On Wed, Nov 5, 2014 at 11:13 PM, Ivan Evstegneev
<webmailgroups at gmail.com> wrote:
> That's what I'm talking about (asking actually), where do you know it from?
> I mean, if there are some resources, which explain all these syntax abbreviations? The general concept.

The best way to find clues about what the conventions mean is to find
something that codifies them in some way. Like this:

http://docopt.org/

That's talking about command-line arguments to an application, but a
lot of the notations are the same.

ChrisA