[PATCH] emacs: add compatability functions for emacs 23

[David Bremner]

Mark Walters <markwalters1009 at gmail.com> writes:

> This is a good point. I think I don't mind too much if they do -- they
> should see it is provided by notmuch-lib if they do describe-function
> etc. But maybe bremner would like to comment?
>
> However, maybe other packages are doing the same. Thus I think we should
> not put in a cut down version of read-char-choice but just include the
> whole command from the emacs24 source. That way if any other package is
> doing the same load order doesn't matter -- we don't stomp on them and
> they don't stomp on us.

There is a sort of precedent with the package cl-lib.el.  Of course it's
not exactly the same since it's mainly providing new names for
functionality that already existed. Quoting from the package description:

,----
| This is a forward compatibility package, which provides (a subset of) the
| features of the cl-lib package introduced in Emacs-24.3, for use on
| previous emacsen.
| 
| Make sure this is installed *late* in your `load-path`, i.e. after Emacs's
| built-in .../lisp/emacs-lisp directory, so that if/when you upgrade to
| Emacs-24.3, the built-in version of the file will take precedence, otherwise
| you could get into trouble (although we try to hack our way around the
| problem in case it happens).
`----

> (As an aside if we do that do we need to include any copyright notice or
> similar? -- maybe notmuch-lib.el could include notmuch-compat.el which
> would contain all the compatability functions?)

We should definitely preserve copyright information (the licensing is
the same, so no problem there)

>> The only other package I have non-trivial experience working with is
>> Gnus, and the practice there was to place portability interfaces in the
>> gnus- namespace, and refrain from calling the "native" interfaces
>> directly.
>
> I think this would introduce a lot of clutter, so I would prefer not to
> go that route.

I don't have strong opinions about that, but note that we're talking
about (currently) 5 lines of code.

d