bug#35344: 26.2; (elisp) `Undo' for `undo-auto-amalgamate'

[Drew Adams <drew.adams@oracle.com>]

This doc does not seem sufficient.  Unlike the doc string, what it says
for `undo-auto-amalgamate' does not seem to describe the function at all.

It seems to try to provide some info about amalgamating, but it does not
tell what this function does (AFAICT).

Please describe this function.  But please also consider explaining how
to use it - that's not clear to me.  Presumably you can use it to group
what would otherwise be separate undo pieces into a single undo chunk.
How to do that is not clear (to me), and there is no distributed Lisp
code that uses it, to refer to as an example.  The only reference made
to its use is to C-coded functions (which are the only distributed
functions that use it).

In GNU Emacs 26.2 (build 1, x86_64-w64-mingw32)
 of 2019-04-13
Repository revision: fd1b34bfba8f3f6298df47c8e10b61530426f749
Windowing system distributor `Microsoft Corp.', version 10.0.17134
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''