Clarify Koji 'repositories' metadata (OSBS-4705)
Clarify Koji 'repositories' metadata (OSBS-4705)

The by-schema1-digest pull specification in the Koji Build archive
metadata refers to an image manifest for the unique tag, not the
version-release tag.

When group_manifests is false, the by-tag pull specification is for the
version-release tag.

However, when group_manifests is true, the by-tag pull specification is
for the unique tag.

For clarity, don't specify which tag is referred to by either by-tag or
by-digest references.

Signed-off-by: Tim Waugh <fe049355006bf7fdd11c5e47ffe7a5032af30704@redhat.com>

DBuildService/atomic-reactor,projectatomic/atomic-reactor,projectatomic/atomic-reactor,DBuildService/atomic-reactor,fr34k8/atomic-reactor,fr34k8/atomic-reactor