bug#32795: bug#32832: [PATCH] Fix 'provided-mode-derived-p' when the parent is an alias

[Eli Zaretskii]

> From: andrew@schwartzmeyer.com
> Date: Mon, 24 Sep 2018 21:09:39 -0700
> 
> From: Andrew Schwartzmeyer <andrew@schwartzmeyer.com>
> 
> Authors of Emacs packages often derive from an alias of a mode instead
> of the mode directly.  This is especially the case when deriving from
> 'prog-mode' as it is relatively new.  Unfortunately, using
> 'derived-mode-p' to check if some mode is derived from an alias of
> 'prog-mode' does not work as expected.  The bug is that
> 'provided-mode-derived-p' should not only return non-nil when MODE is
> one of MODES, but also when MODE is an alias of one of MODES.
> * lisp/subr.el (provided-mode-derived-p):
> Return non-nil when MODE is an alias of any of MODES (Bug#32795).
> * test/lisp/subr-tests.el: Add tests for the above.

Thanks, pushed.

In the future please either format your patches with "git
format-patch" or make sure the first line of the commit log message is
a single sentence followed by an empty line (this is explained in
CONTRIBUTE), to make the patch application easier.

Also, you don't seem to have a copyright assignment on file, and this
contribution comes close to exhausting the amount of changes we can
accept without such an assignment.  So I urge you to start your legal
paperwork rolling, to allow us to accept more contributions from you.
If you are interested, I will send you the assignment form off-list.