bug#7567: Please add a history variable to read-regexp

[Drew Adams]

> > Also take care of the strange query-replace-from-history-variable in
> > read-regexp.
> 
> No answer. Was something unclear here?
> 
> The current read-regexp use is problematic for example in
> multi-isearch-read-matching-buffers and
> multi-occur-in-matching-buffers. I think a common history variable
> could be used for those cases, but they currently use the default
> regexp-history variable which seems totally inappropriate.

I don't mean to meddle here, but it's not clear to me why `regexp-history' is
not appropriate in the contexts you mention.  The user is inputting a regexp.
Why shouldn't previous regexps the user inputted be available in the input
history for this operation?