bug#2137: 23.0.60; Saving Rmail buffer does not show the "Saving file ..." message

[Richard M Stallman <rms@gnu.org>]

    > IMO, using annotations for the job of saving the mailbox is also a
    > horrible kludge.  All that just to avoid defining an Rmail-specific
    > binding for C-x C-s ...

    Thanks for your support,

An Rmail-specific binding for C-x C-s is not enough to make saving
work correctly.  Users can save the file through C-x s also, and other
commands too.  The common mechanism for these commands is
`save-buffer'; whatever makes them save the right text has to work
inside there.

Eli wrote:

     we could add to
    rmail-write-region-annotate another hack: a call to buffer-size
    followed by the same message "Saving file ..." that should have been
    displayed by save-buffer.

The difficulty here is to display that message only in the case
where the hook was ultimately called from `save-buffer'.  This could
be done by making `save-buffer' bind some variable for such hooks
to check.

However, such fixes are less clean that implementing `buffer-swapped-with'
and checking it in the necessary places.  I previously implemented it in
`basic-save-buffer', but just moving the implementation to `save-buffer'
would make it DTRT for this.  The fix would add no complexity.

    The simplest fix is to simply always output the message rather than only
    for files larger than 50KB.

That would be easy, but not quite the most convenient behavior.

    The more difficult one is to move the message from save-buffer to
    write-region.