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, 3 insertions, 3 deletions

diff --git a/doc/lispref/backups.texi b/doc/lispref/backups.texi
index 6a5b6d1661d..c17d98eb190 100644
--- a/doc/lispref/backups.texi
+++ b/doc/lispref/backups.texi
@@ -232,11 +232,11 @@ non-@code{nil}.
 @defopt backup-by-copying-when-privileged-mismatch
 This variable, if non-@code{nil}, specifies the same behavior as
 @code{backup-by-copying-when-mismatch}, but only for certain user-id
-values: namely, those less than or equal to a certain number.  You set
-this variable to that number.
+and group-id values: namely, those less than or equal to a certain number.
+You set this variable to that number.
 
 Thus, if you set @code{backup-by-copying-when-privileged-mismatch}
-to 0, backup by copying is done for the superuser only,
+to 0, backup by copying is done for the superuser and group 0 only,
 when necessary to prevent a change in the owner of the file.
 
 The default is 200.