bug#3016: 23.0.92.2; offer to make a directory when saving if it is needed

[Glenn Morris <rgm@gnu.org>]

Kazuhiro Ito wrote:

> I want this check is done more later.  Because, in draft buffers of
> Wanderlust (a message user agent), buffer-file-name does not indicate
> actual file name and saving file is done via hook functions (such as
> write-contents-functions, local-write-file-hooks,
> write-file-functions).  In such case, this offer could make incorrect
> directory.

My initial reaction is to ask why you can't just set buffer-file-name to
the right value (or to nil, so that basic-save-buffer will prompt for
it); or at least to something whose parent directory exists, and then do
whatever checks you want in your hook functions?

By doing it the way you do, it sounds like you must already be missing
the other checks that basic-save-buffer does (overwriting an existing
file, saving to a directory rather than a file, verify file modtime),
though they may not be relevant in your case.