Click states that it "fully follows the Unix command line conventions" (on http://click.pocoo.org/6/why/).

Because lateron it refers to "POSIX compliant argument handling", I assume that this means that click conforms to 12.2 "Utility Syntax Guidelines" in POSIX.1-2008 (http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap12.html#tag_12_02).

These guidelines however do not cover long options names at all.

It would be good if Click in its documentation clearly described the implemented command line conventions. This can be done for example by providing a reference to some other document plus describing any deviations or additions.