This is a followup to #18839. That PR relaxed the fallback logic so that
if a manifest doesn't exist on v2, or the user is unauthorized to access
it, we try again with the v1 protocol. A similar special case is needed
for "pull all tags" (docker pull -a). If the v2 registry doesn't
recognize the repository, or doesn't allow the user to access it, we
should fall back to v1 and try to pull all tags from the v1 registry.
Conversely, if the v2 registry does allow us to list the tags, there
should be no fallback, even if there are errors pulling those tags.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
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