Documentation: update tar.umask default

As noted by Mike Hommey, the documentation for the config setting tar.umask
is not up-to-date.  Commit f08b3b0e2e9ad87767d80ff03b013c686e08ba4b changed
the default from 0 to 2; this patch finally documents it.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-archive.txt b/Documentation/git-archive.txt
index 4da07c1..f2080eb 100644
--- a/Documentation/git-archive.txt
+++ b/Documentation/git-archive.txt
@@ -72,16 +72,13 @@
 
 CONFIGURATION
 -------------
-By default, file and directories modes are set to 0666 or 0777 in tar
-archives.  It is possible to change this by setting the "umask" variable
-in the repository configuration as follows :
 
-[tar]
-        umask = 002	;# group friendly
-
-The special umask value "user" indicates that the user's current umask
-will be used instead. The default value remains 0, which means world
-readable/writable files and directories.
+tar.umask::
+	This variable can be used to restrict the permission bits of
+	tar archive entries.  The default is 0002, which turns off the
+	world write bit.  The special value "user" indicates that the
+	archiving user's umask will be used instead.  See umask(2) for
+	details.
 
 EXAMPLES
 --------