Add an optional parameter to kill-all-local-variables

* doc/lispref/variables.texi (Creating Buffer-Local): Document it
(bug#30204).

* src/buffer.c (Fkill_all_local_variables): Allow killing
permanent local variables, too.

* src/print.c (temp_output_buffer_setup):
* src/minibuf.c (set_minibuffer_mode): Adjust callers.

1 files changed, 7 insertions, 5 deletions

diff --git a/doc/lispref/variables.texi b/doc/lispref/variables.texi
index a1d1919b4bf..d2247004bcb 100644
--- a/doc/lispref/variables.texi
+++ b/doc/lispref/variables.texi
@@ -1695,12 +1695,14 @@ buffer-local variables interactively.
 @end deffn
 
 @cindex local variables, killed by major mode
-@defun kill-all-local-variables
+@defun kill-all-local-variables &optional kill-permanent
 This function eliminates all the buffer-local variable bindings of the
-current buffer except for variables marked as permanent and local
-hook functions that have a non-@code{nil} @code{permanent-local-hook}
-property (@pxref{Setting Hooks}).  As a result, the buffer will see
-the default values of most variables.
+current buffer.  As a result, the buffer will see the default values
+of most variables.  By default, for variables marked as permanent and
+local hook functions that have a non-@code{nil}
+@code{permanent-local-hook} property (@pxref{Setting Hooks}) won't be
+killed, but if the optional @var{kill-permanent} argument is
+non-@code{nil}, even these variables will be killed.
 
 This function also resets certain other information pertaining to the
 buffer: it sets the local keymap to @code{nil}, the syntax table to the