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.
+ mkdir t
+ cd t
+ hg init
+ echo a
+ hg add a
+ hg commit -m test -d '0 0'
+ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
+ hg parents
changeset: 0:acb14030fe0a
tag: tip
user: test
date: Thu Jan 1 00:00:00 1970
summary: test
+ hg status
+ hg undo
rolling back last transaction
+ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
0 files, 0 changesets, 0 total revisions
+ hg parents
+ hg status
A a