Move commands.forget over to using new walk code.
With no names, it now recursively forgets everything, as is the default
behaviour of other commands. And prints the names of all files it
hasn't specifically been told to forget.
#!/bin/sh
set -ex
mkdir test
cd test
echo foo>foo
hg init
hg addremove
hg commit -m "1"
hg verify
hg clone . ../branch
cd ../branch
hg co
echo bar>>foo
hg commit -m "2"
cd ../test
hg pull ../branch
hg verify
hg co
cat foo
hg manifest