Document the -n command-line option to git-unpack-objects

This patch documents the -n command-line option to git-unpack-objects,
as it was previously undocumented.

Signed-off-by: Nikolai Weibull <nikolai@bitwi.se>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/Documentation/git-unpack-objects.txt b/Documentation/git-unpack-objects.txt
index b716ba1..31ea34d 100644
--- a/Documentation/git-unpack-objects.txt
+++ b/Documentation/git-unpack-objects.txt
@@ -8,7 +8,7 @@
 
 SYNOPSIS
 --------
-'git-unpack-objects' [-q] <pack-file
+'git-unpack-objects' [-n] [-q] <pack-file
 
 
 DESCRIPTION
@@ -19,6 +19,10 @@
 
 OPTIONS
 -------
+-n::
+        Only list the objects that would be unpacked, don't actually unpack
+        them.
+
 -q::
 	The command usually shows percentage progress.  This
 	flag suppresses it.