backup-by-copying-when-privileged-mismatch applies to file gid, too.

* lisp/files.el (backup-by-copying-when-privileged-mismatch):  In addition
to checking the file uid, a second test is added: if the file gid is not
greater than backup-by-copying-when-privileged-mismatch,
backup-by-copying-when-mismatch will also be forced on.

* doc/emacs/files.texi, doc/lispref/backups.texi: Updated documentation.

Also fixed a typo in the Emacs reference manual, changing "higher" to
"no greater" so that the limit is no longer documented reversed.

1 files changed, 5 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 6e0b039ce30..678139ecbcf 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -533,6 +533,11 @@ The HIST argument of 'read-from-minibuffer' now works correctly with
 buffer-local variables.  This means that different buffers can have
 their own separated input history list if desired.
 
+** 'backup-by-copying-when-privileged-mismatch' applies to file gid, too.
+In addition to checking the file owner uid, Emacs also checks that the
+group gid is not greater than backup-by-copying-when-privileged-mismatch;
+if so, backup-by-copying-when-mismatch will be forced on.
+
 
 * Editing Changes in Emacs 27.1