[PATCH] Fix git-checkout-script exit status

Sometimes the git-read-tree in git-checkout-script fails for me.
Make sure that the failed status is passed up to caller.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-checkout-script

@@ -72,4 +72,6 @@ if [ "$?" -eq 0 ]; then
 	fi
 	[ "$branch" ] && ln -sf "refs/heads/$branch" "$GIT_DIR/HEAD"
 	rm -f "$GIT_DIR/MERGE_HEAD"
+else
+	exit 1
 fi