umoci 0.0.0~rc3

umoci has now gone a large amount of cleanup, and included the addition
of a few previously missing features. The main thing blocking a full
release is that manifest lists are still unsupported, and there are some
upstream PRs that define some of umoci's operations that need to be
merged before umoci can be considered a compliant implementation. In
addition, the logging library needs to be swapped (and the amount of
output reduced).

Here's a short list of features added:

• xattr support for both packing and unpacking was added, in particular
  this code also handles the issue of security.selinux. More policy
  decisions need to be added, but those are being discussed upstream.
  cyphar/umoci#52 cyphar/umoci#49
• Ensure that environment variables have no duplicates. This ensures
  that umoci won't duplicate environment variables in either Config.Env
  or the extracted process.env. cyphar/umoci#30
• Add support for read-only CAS operations with a read-only filesystem.
  Previously, attempting to open an OCI image on a read-only filesystem
  would fail miserably, now you can do read-only operations without
  issue. cyphar/umoci#47
• Garbage collection now also garbage collects old tmpdirs, and other
  garbage from inside an image layout. cyphar/umoci#17
• Output a helpful comment about --rootless if you're getting EPERMs.
• Enable stack traces from an error if the --debug flag was applied to
  umoci. This is a feature that hopefully will be added to pkg/errors
  upstream.
• Cleanups to vendoring of go-mtree so that it's much more
  upstream-friendly.

Signed-off-by: Aleksa Sarai [email protected]