bug#52896: 29.0.50; transient-mark-mode is set to a lot of 'only syms

[Andrey Listopadov]

> That's true, but in "emacs -Q", once I use a non-shifted command, the
> value becomes just nil, as intended.

Here's how to reproduce this without expand-region in `emacs -Q'

1. `M-x transient-mark-mode RET' - disabling tmm;
2. Shift-right on some word in the *scratch* buffer - initial `only'
is consed to `transient-mark-mode';
3. `C-x C-x' `C-x C-x' `C-x C-x' to invoke the
`exchange-point-and-mark' function several times;
4. `C-h v transient-mark-mode RET' - the value is `(only only only only only)'.

So I guess this is the `exchange-point-and-mark' issue.

-- 
Andrey Listopadov