Subject: Updates to the latest {diff,merge}tool series

From: David Aguilar <[email-masked]>
Date: Tue, 7 Apr 2009 01:21:18 -0700

Here they are.

07/14: Updated usage synopsis
09/14: Updated diff.tool config.txt documentation
10/14: The original broke the test suite on Mac OS...
       Testing {diff,merge}tool.<tool>.path is tricky.
11/14: This depends on 07/14, so the rebase requires a resend
14/14: Reworked logic as discussed.