Fix potential command line overflow in hooks--update

In a repository with a large number of refs, the following command line
could easily overflow the command line size limitations

 git-rev-list $newref $(git-rev-parse --not --all)

Fortunately, git-rev-list already has the means to cope with this
situation with the --stdin switch

 git-rev-parse --not --all | git-rev-list --stdin $newref

Which is exactly what this patch does.

Signed-off-by: Andy Parkins <andyparkins@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

templates/hooks--update

@@ -148,7 +148,7 @@ case "$refname_type" in
 			# This shows all log entries that are not already covered by
 			# another ref - i.e. commits that are now accessible from this
 			# ref that were previously not accessible
-			git-rev-list --pretty $newref $(git-rev-parse --not --all)
+			git-rev-parse --not --all | git-rev-list --stdin --pretty $newref
 			echo $LOGEND
 		else
 			# oldrev is valid