tests: add test for widening from an empty clone
Narrow clones that track no paths currently don't even include the
root manifest (which is the only manifest when using flat
manifests). That means that when we widen from such a clone, we need
to make sure that we send the root manifest (and other manifests if
using tree manifests). That currently works because we always resend
all manifest that match the new narrowspec. However, we're about to
stop resending manifests that the client already has and there's a
risk of this breaking then, so let's add a test.
Differential Revision: https://phab.mercurial-scm.org/D5143
[workspace]
members = ["hgcli", "hg-core", "hg-direct-ffi"]
exclude = ["chg"]