Re: Obtaining a database of new functionality per Emacs version

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 7 Dec 2020 18:50:07 +0100
> From: Vasilij Schneidermann <mail@vasilij.de>
> Cc: emacs-devel@gnu.org
> 
> > Did you try "make TAGS" in the top-level directory, followed by
> > searching the TAGS files?
> 
> Thanks, that's the kind of idea I'm looking for. I'd still need to diff
> that output against that of an older Emacs version to find out what has
> been removed/added between the releases, but that's fine. Another
> problem is that it includes helper functions that aren't part of a
> public API.

I thought the latter problem will not be an issue in your case, since
my mental model of what you want was that you have a function in hand
and want to check whether it was available in Emacs XX.YY.  In which
case you will never need to look for internal functions.

> > Manually or automatically?  If manually, the result will be as
> > accurate and comprehensive as NEWS.  If automatically, please tell
> > what kind of implementation you have in mind.
> 
> Manually, similar to how version information is added to customizables.

That needs Someone™ to be extra vigilant and double-check any changes
that add functions to prod people to mark them with a version tag.  My
experience with being that cop in defcustoms case is that the
probability of some falling through the cracks is non-negligible.

> The gain is having a machine-readable version you can consult from a
> Lisp program. Who knows, maybe you could use it to make an Emacs Lisp
> spec independent implementations could target...

I know of libraries that have this as part of their SOPs, but Emacs is
so much larger than any library that I doubt if this scales well
enough.  So I don't believe such manual procedures will be reliable
enough in Emacs.  One possible idea is to have a Git commit hook that
would reject commits with new functions if they fail to include the
necessary tag.