Fix "C-u M-!" when 'shell-command-dont-erase-buffer' is non-nil

* lisp/simple.el (shell-command-dont-erase-buffer): Clarify the
effect of the various values in the doc string.
(shell-command-save-pos-or-erase, shell-command): Don't move or
push point if the output will go to the current buffer.
(Bug#40690)
(shell-command): Mention 'shell-command-dont-erase-buffer' in the
doc string.

* test/lisp/simple-tests.el
(with-shell-command-dont-erase-buffer): Don't is shell quoting
'like this', as it doesn't work on MS-Windows; quote "like this"
instead.
(simple-tests-shell-command-dont-erase-buffer): Adapt the test to
the new modus operandi.

* doc/emacs/misc.texi (Single Shell): Document the effect of the
various values of 'shell-command-dont-erase-buffer'.

* etc/NEWS: Expand and reword the entry regarding changes in
'shell-command-dont-erase-buffer'.

1 files changed, 8 insertions, 3 deletions

diff --git a/etc/NEWS b/etc/NEWS
index aba3028184b..4485bf91650 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2084,12 +2084,17 @@ variable for remote shells.  It still defaults to "/bin/sh".
 ** Single shell commands
 
 +++
-*** 'shell-command-dont-erase-buffer' accepts the value 'erase' to
-force to erase the output buffer before execution of the command.
+*** New values of 'shell-command-dont-erase-buffer'.
+This option can now have the value 'erase' to force to erase the
+output buffer before execution of the command, even if the output goes
+to the current buffer.  Additional values 'beg-last-out',
+'end-last-out', and 'save-point' control where to put point in the
+output buffer after inserting the shell-command output.
 
+---
 *** The new functions 'shell-command-save-pos-or-erase' and
 'shell-command-set-point-after-cmd' control how point is handled
-between two consecutive shell commands in the same buffer.
+between two consecutive shell commands in the same output buffer.
 
 +++
 *** 'async-shell-command-width' defines the number of display columns