* doc/lispref/text.texi (Atomic Changes): Mention
undo-amalgamate-change-group (bug#42303).
@defun cancel-change-group handle
This function cancels and undoes all the changes in the change group
specified by @var{handle}.
+@end defun
+
+@defun undo-amalgamate-change-group
+Amalgamate changes in change-group since @var{handle}. I.e., remove
+all undo boundaries between the state of @var{handle} and now.
@end defun
Your code should use @code{unwind-protect} to make sure the group is