(Evil) Unimplemented ex command (marks)

[Óscar Fuentes]

When I type :marks Evil shows

Unknown command: `marks'

but evil-maps.el contains

(evil-ex-define-cmd "marks" 'evil-show-marks)

evil-show-maps is not defined anywhere.

Why? I can think of three possible answers:

1. Nobody cares. Vim users can remember all their markers.

2. It is useful, but difficult to implement.

3. None of the above. Patches welcome :-)

Of course, the answer might be something else.

My interest on `marks' was prompted by someone publishing an extension
for Emacs that, after a customizable delay, pops up a list of defined
registers when you invoke a register-related command. I'll like to do
the same for Evil's registers and markers.