tests/test-backwards-remove.t

wireprotov2: expose rich arguments metadata

Now that we internally store rich metadata about arguments, it makes
sense to make that metadata available to the client. This will allow
clients to validate outgoing command requests before they are sent
over the wire.

Strictly speaking, we should bump the wire protocol version for this
change since it is backwards incompatible. But no client-side code
touches the arguments map and I don't want to incur the work.

Differential Revision: https://phab.mercurial-scm.org/D4618

  $ hg init
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ ls
  a
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ hg co 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

B should disappear

  $ ls
  a