bug#26871: 25.2; Support revert-buffer for Customize buffers

[Phil Sainty]

On 11/05/17 11:01, Drew Adams wrote:
> https://emacs.stackexchange.com/q/32714/105
> shows that at least one user expected existing Customize buffers to
> auto-revert.  This enhancement request will help in that direction
> (not automatic, but that's OK).

That question did indeed prompt this, but I've been meaning to raise
it for a long time.

It can be particularly confusing when the buffer exists but is not
displayed, as if you invoke the customize command in that scenario,
the behaviour *appears* to be the same as if the buffer had not
already existed, but that's not actually the case, and it might be
showing you stale data.

That's also slightly tangential to the stated feature request, but
revert-buffer support again seems like the logical first step.