[PATCH] make dotest more amenable to commit message editing

[PATCH] make dotest more amenable to commit message editing

This makes "dotest" a lot nicer to sue, especially for people who were
used to editing the commit comments after-the-fact in BK, which git
doesn't apply.

he syntax is

	dotest [-q] mailbox [signoff]

so the command line operates exactly as you're used to.  If you supply
the -q it will query before applying (I also added the [a]pply all the
rest option).  If the signoff file is absent, no signoff line gets
added.

There's also one addition in this:  a checkout-cache line.  I added that
for poor saps like me whose laptop takes minutes to checkout a full
build tree, so I can run dotest in a directory with no checked out
files.