RE: how to get key maps info?

[Drew Adams]

> > the C-h k describe a specific key, so that C-h k M-g g 
> > provides me the documentation for goto-line. But what if
> > I want to get all the possible completion for M-g?
> > Is there an help feature for that?
> 
> In most situations, <prefix keys> C-h will do it, so that 
> would be `M-g C-h' in this case.

That is a good answer, but there are some cases where it doesn't
work.  (I don't recall particular cases.  Isearch used to be one,
but that has been corrected.)

Other things that can help in this way:

1. `C-h b' and `C-h m' (which have already been mentioned).

2. `C-h M-k' to see all the bindings for a particular keymap.
Requires library `help-fns+.el'.  E.g., `C-h M-k ctl-x-map'.
This is especially useful for keymaps, such as minibuffer maps,
that you cannot easily examine otherwise.

3. `<prefix key> S-TAB' to complete the key sequence.  Requires
library `icicles.el'.  E.g., `M-g TAB' shows these completions:

..                       c  =  goto-char     ESC  =  ...
g  =  goto-line          M-g  =  goto-line   M-n  =  next-error
M-p  =  previous-error   n  =  next-error    p  =  previous-error
TAB  =  move-to-column

(`..' goes up a level, in this case above prefix key `M-g' to
the top.  `...' indicates here that ESC (i.e., `M-g M-') is
itself a prefix key.) 

This shows you the available keys, but it also lets you invoke
them.  It is the equivalent, for keys, of completing a command
name when you use `M-x'.

During key completion, if you cycle among candidates then the
mode line of window *Completions* shows the first line of what
`C-h k' would show for the current candidate key.  `C-M-RET'
shows the full `C-h k' help for the current candidate key.

Info about #2 and #3:
http://www.emacswiki.org/emacs/HelpPlus
http://www.emacswiki.org/emacs/Icicles_-_Key_Completion