Fix permissions bugs with setgid directories etc.

* configure.ac (BSD4_2): Remove; no longer needed.
* admin/CPP-DEFINES (BSD4_2): Remove.
* doc/lispintro/emacs-lisp-intro.texi (Files List):
directory-files-and-attributes now outputs t for attribute that's
now a placeholder.
* doc/lispref/files.texi (Testing Accessibility): Document GROUP arg
of file-ownership-preserved-p.
(File Attributes): Document that 9th element is now
just a placeholder.
* doc/lispref/os.texi (User Identification): Document new functions group-gid,
group-real-gid.
* etc/NEWS: Document changes to file-attributes,
file-ownership-preserved-p.
Mention new functions group-gid, group-real-gid.
* lisp/files.el (backup-buffer): Don't rely on 9th output of
file-attributes, as it's now a placeholder.  Instead, use the new
optional arg of file-ownership-preserved-p.
(file-ownership-preserved-p): New optional arg GROUP.
Fix mishandling of setuid directories that would cause this
function to return t when it should have returned nil.
Document what happens if the file does not exist, and when
it's not known whether the ownership will be preserved.
* lisp/net/tramp-sh.el (tramp-sh-handle-file-ownership-preserved-p):
Likewise.
(tramp-get-local-gid): Use group-gid for integer, as that's
faster and more reliable.
* src/dired.c (Ffile_attributes): Return t as the 9th attribute,
to mark it as a placeholder.  The old value was often wrong.
The only user of this attribute has been changed to use
file-ownership-preserved-p instead, with its new group arg.
* src/editfns.c (Fgroup_gid, Fgroup_real_gid): New functions.

Fixes: debbugs:13125

2 files changed, 18 insertions, 0 deletions

diff --git a/etc/ChangeLog b/etc/ChangeLog
index ad0f9e9c7e8..7d58a670f80 100644
--- a/etc/ChangeLog
+++ b/etc/ChangeLog
@@ -1,3 +1,10 @@
+2012-12-14  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Fix permissions bugs with setgid directories etc. (Bug#13125)
+        * NEWS: Document changes to file-attributes,
+        file-ownership-preserved-p.
+        Mention new functions group-gid, group-real-gid.
+
 2012-12-06  Andreas Schwab  <schwab@linux-m68k.org>
 
         * themes/leuven-theme.el: Convert to Unix format.
diff --git a/etc/NEWS b/etc/NEWS
index 9f61cff7342..d2a85507034 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -166,6 +166,17 @@ text-property on the first char.
 ** The `defalias-fset-function' property lets you catch calls to defalias
 and redirect them to your own function instead of `fset'.
 
+** The 9th element returned by `file-attributes' is now unspecified.
+Formerly, it was t if the file's gid would change if file were deleted
+and recreated.  This value has been inaccurate for years on many
+platforms, and nobody seems to have noticed or cared.
+
+** The function `file-ownership-preserved-p' now has an optional
+argument GROUP which causes it check for file group too.  This can be
+used in place of the 9th element of `file-attributes'.
+
+** New functions `group-gid' and `group-real-gid'.
+
 * Changes in Emacs 24.4 on non-free operating systems
 
 +++