I agree with Drew's reasoning behind not using up the M-s b/f bindings for
occur-backward/forward. But I don't like the idea of having M-s o as a
submap binding. M-s o is super useful as it is now.

Here's a suggestion for bindings that might work out. I am not at a
computer, so cannot verify if M-s M-o is already taken,.. but if not then
how about

M-s M-o f for occur-forward, and
M-s M-o b for occur-backward

??

The above bindings are easy to press and also easy to remember.

On Thu, Dec 29, 2016, 11:47 PM Drew Adams <drew.adams@oracle.com> wrote:

> >  (define-key search-map "o"    'occur)
> > +(define-key search-map "b"    'occur-backward)
> > +(define-key search-map "f"    'occur-forward)
>
> FWIW, I don't think those keys (`M-s b' and `M-s f') should be
> bound to those commands.  If we want to bind the new commands
> during Isearch then I suggest that the occur commands be grouped
> on prefix key `M-s o':
>
>   M-s oo   occur
>   M-s ob   occur-backward
>   M-s of   occur-backward
>
> `M-s' is a _general_ search prefix key.  There is nothing
> particularly mnemonic about `b' or `f' being `occur-backward'
> or `occur-forward'.  And we should not sacrifice 3 `M-s' keys
> to these commands.
>
> I, and perhaps other users, and perhaps in the future vanilla
> Emacs, have other bindings on `M-s'.  And `M-s' bindings can
> be anything at all related to the encompassing context of
> searching.
>
> --

Kaushal Modi