bug#42842: 27.0.91; indent-rigidly deactivates the mark with no visual cues

[Nicolas Richard]

C-x TAB deactivates the mark before running any other command.
I don't think it's appropriate :

    if I use C-x TAB <right> <right>
    
    then I can see the mark is still active (the region is highlighted).
    
    but if I now use a command which uses the active region (e.g. M-% or
    TAB),
    
    it doesn't act on the region anymore.
    
    
    The reason is that `indent-rigidly' runs deactivate-mark before
    leaving
    
    transient map:
    
    (set-transient-map indent-rigidly-map t #'deactivate-mark)

It was introduced in 9ae89c2c99c (which fixes bug #20408).

    My suggestion is to either revert 9ae89c2c99c or add a note in the
    
    docstring, e.g :
    
    
    > Typing any other key deactivates the transient mode. If
    
    > transient-mark-mode is enabled, it also deactivates the mark.
    It can
    
    > be reactivated using \\[exchange-point-and-mark]
    
    
    
    
    In GNU Emacs 27.0.91 (build 2, x86_64-pc-linux-gnu, GTK+ Version
    2.24.30)
    
    of 2020-07-07 built on user-ThinkPad-T400
    
    Repository revision: 247dcb4b1b1b4ea3d50b63d41c4efa58743f610d
    
    mRepository branch: emacs-27
    
    Windowing system distributor 'The X.Org Foundation', version
    11.0.11804000
    
    System Description: Trisquel GNU/Linux Flidas (8.0)