Plain copy-file no longer chmods an existing destination.

* doc/lispref/files.texi (Changing Files): Document this.
* etc/NEWS: Document this.
* src/fileio.c (realmask): Now a static var, not a local.
(barf_or_query_if_file_exists): New arg KNOWN_TO_EXIST.
Remove arg STATPTR.  All uses changed.
(Fcopy_file): Do not alter permissions of existing destinations,
unless PRESERVE-PERMISSIONS (renamed from
PRESERVE-EXTENDED-ATTRIBUTES) is non-nil.
Avoid race when testing for existing destinations and for
when input and output files are the same.
If changing the group fails, adjust both default and
preserved permissions so that access is not granted to the
wrong group.
(Fset_default_file_modes, init_fileio): Update realmask.
(Fdefault_file_modes): Use realmask instead of calling umask.

Fixes: debbugs:16133

2 files changed, 10 insertions, 6 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 2ebab695514..3de4ae598fe 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2013-12-29  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Plain copy-file no longer chmods an existing destination (Bug#16133).
+        * files.texi (Changing Files): Document this.
+
 2013-12-28  Chong Yidong  <cyd@gnu.org>
 
         * modes.texi (Auto Major Mode): Document interpreter-mode-alist
diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index c1eae5eefa3..01eef350ddf 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -1563,8 +1563,6 @@ some operating systems.)  If setting the time gets an error,
 interactive call, a prefix argument specifies a non-@code{nil} value
 for @var{time}.
 
-This function copies the file modes, too.
-
 If argument @var{preserve-uid-gid} is @code{nil}, we let the operating
 system decide the user and group ownership of the new file (this is
 usually set to the user running Emacs).  If @var{preserve-uid-gid} is
@@ -1572,10 +1570,11 @@ non-@code{nil}, we attempt to copy the user and group ownership of the
 file.  This works only on some operating systems, and only if you have
 the correct permissions to do so.
 
-If the optional argument @var{preserve-extended-attributes} is
-non-@code{nil}, and Emacs has been built with the appropriate support,
-this function attempts to copy the file's extended attributes, such as
-its SELinux context and ACL entries (@pxref{File Attributes}).
+If the optional argument @var{preserve-permissions} is non-@code{nil},
+this function copies the file's permissions, such as its file modes,
+its SELinux context, and ACL entries (@pxref{File Attributes}).
+Otherwise, if the destination is created its file permission bits are
+those of the source, masked by the default file permissions.
 @end deffn
 
 @deffn Command make-symbolic-link filename newname  &optional ok-if-exists