RE: Multiple M-x shells sharing input ring

[Drew Adams <drew.adams@oracle.com>]

> > I don't see how anything in that description applies here.  Maybe
> > the description is faulty.  Or maybe this variable should not be
> > permanent-local.  But so far, the description does not seem (to
> > me) to fit the `comint-input-history' case.
> 
> permanent-local is used to mark variables as pertaining to the
> content of a buffer rather than to its mode.

So presumably that doc should be changed to speak of "the buffer"
instead of "the file".  The sentence you just wrote is clearer
than what is in the doc, IMO.

> The effect it has is that the variable won't be reset if you
> change major mode (i.e. it's not "killed" by kill-local-variables).
> 
> It's reasonably common in comint buffer to reset the major mode
> (typically, you kill the process and re-run it which sets up the
> comint mode again) and you generally want to preserve the
> input-history, hence the `permanent-local' property.

I see.  Yes, I guess that makes sense.  It is a use case that
is perhaps worth pointing out in the doc.

> Note also that the `permanent-local' property does not make a
> variable buffer-local.  It just makes it stay local longer, in
> case it was made local.

I see.  I thought it also made the variable buffer-local.