Usage: rebar comment <ticket_id> <body>

Append a comment to a ticket. The body is a SINGLE positional argument — this
command takes no options, so there is no --body / --body-file form; an
option-looking argument is rejected rather than stored as the body.

For a long body, substitute a file's contents in the shell:
  rebar comment <ticket_id> "$(cat /path/to/body.md)"

If the body itself begins with "-", end option parsing with "--" first:
  rebar comment <ticket_id> -- "-starts with a dash"
