Change order of -m option to update-ref.

The actual position doesn't matter but most people prefer to see
options appear before the arguments.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-update-ref.txt

@@ -7,7 +7,7 @@ git-update-ref - update the object name stored in a ref safely
 
 SYNOPSIS
 --------
-'git-update-ref' <ref> <newvalue> [<oldvalue>] [-m <reason>]
+'git-update-ref' [-m <reason>] <ref> <newvalue> [<oldvalue>]
 
 DESCRIPTION
 -----------