In unit tests that create a SystemContext, point that SystemContext at
the testing signature policy and registries configuration. This should
cause us to pay attention to mirroring settings for images used by this
set of tests.
Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
Add API for adding arbitrary layers at commit-time via CommitOptions,
and via methods of the Builder type.
Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
