In many versions of Emacs the sexp below

  (save-window-excursion (shell) (buffer-name (current-buffer)))

returns "*shell*", but in some recent versions it returns the name of
the current buffer instead.

Let me be more precise. I ran the sexp below in the versions of Emacs
that I have in my machine,

  (list emacs-version
    (save-window-excursion (shell) (buffer-name (current-buffer)))
    )

and collected the outputs, and got:

  ("24.5.1" "*shell*")
  ("25.1.1" "*shell*")
  ("26.3" "*shell*")
  ("27.0.50" "TODO")

Here's the exact version of my "27.0.50". The output of

  PAGER=cat git log -1 --format=format:"%H%n%cd%n"

was:

  01ea96b5548a80e6aabc69428439113ce0a8c17e
  Mon Oct 14 08:47:02 2019 +0200

I don't know (yet) how to bisect versions to find exactly when the
behavior changed, sorry... btw, this is a Debian box (on amd64).

  Cheers,
    Eduardo Ochs
    http://angg.twu.net/#eev