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

[Drew Adams]

> Thanks for asking, I thought it was clear.

You're welcome.

> Why should that regexp be used to make buffer names? It is probably a
> regexp that has been used for matching strings in buffers.

Why is it "probably" that?

I use regexps interactively all over the place.  Matching text in a buffer is
only one use.

> (It might of course be a regexp from a search in *Buffer List*,
> but that is not the normal case.)

IMO, there is no "normal" case.

This is a general limitation wrt history vars.  But it cannot really be
otherwise.  You might want some particular values to be available on a given
history list in some context, and you (or I) might want them to not be available
on that list in another context.

We can add more history vars to get finer-grained control, but then you miss out
if you want to access something that it was decided should be on another history
list.

It's impossible to have it both ways, because the user's intention is a variable
that cannot easily and always be taken into consideration.  IOW, there are some
things the programmer can decide when writing the function call that reads input
(you can use any history var you want, including new ones), but still you cannot
always know what the user really needs/wants.