umoci 0.4.0

• umoci repack now supports --refresh-bundle which will update the
  OCI bundle's metadata (mtree and umoci-specific manifests) after packing the
  image tag. This means that the bundle can be used as a base layer for
  future diffs without needing to unpack the image again. openSUSE/umoci#196
• Added a website, and reworked the documentation to be better structured. You
  can visit the website at umo.ci. openSUSE/umoci#188
• Added support for the user.rootlesscontainers specification, which allows
  for persistent on-disk emulation of chown(2) inside rootless containers.
  This implementation is interoperable with @AkihiroSuda's PRoot
  fork (though we do not test its interoperability at the
  moment) as both tools use the same protobuf
  specification. openSUSE/umoci#227
• umoci unpack now has support for opaque whiteouts (whiteouts which remove
  all children of a directory in the lower layer), though umoci repack does
  not currently have support for generating them. While this is technically a
  spec requirement, through testing we've never encountered an actual user of
  these whiteouts. openSUSE/umoci#224 openSUSE/umoci#229
• umoci unpack will now use some rootless tricks inside user namespaces for
  operations that are known to fail (such as mknod(2)) while other operations
  will be carried out as normal (such as lchown(2)). It should be noted that
  the /proc/self/uid_map checking we do can be tricked into not detecting
  user namespaces, but you would need to be trying to break it on purpose.
  openSUSE/umoci#171 openSUSE/umoci#230

• Fix a bug in our "parent directory restore" code, which is responsible for
  ensuring that the mtime and other similar properties of a directory are not
  modified by extraction inside said directory. The bug would manifest as
  xattrs not being restored properly in certain edge-cases (which we
  incidentally hit in a test-case). openSUSE/umoci#161 openSUSE/umoci#162
• umoci unpack will now "clean up" the bundle generated if an error occurs
  during unpacking. Previously this didn't happen, which made cleaning up the
  responsibility of the caller (which was quite difficult if you were
  unprivileged). This is a breaking change, but is in the error path so it's
  not critical. openSUSE/umoci#174 openSUSE/umoci#187
• umoci gc now will no longer remove unknown files and directories that
  aren't flock(2)ed, thus ensuring that any possible OCI image-spec
  extensions or other users of an image being operated on will no longer
  break. openSUSE/umoci#198
• umoci unpack --rootless will now correctly handle regular file unpacking
  when overwriting a file that umoci doesn't have write access to. In
  addition, the semantics of pre-existing hardlinks to a clobbered file are
  clarified (the hard-links will not refer to the new layer's inode).
  openSUSE/umoci#222 openSUSE/umoci#223

---

Thanks to all of the contributors that made this release possible:

• Aleksa Sarai asarai@suse.de
• Jonathan Boulle jonathanboulle@gmail.com
• Serge Hallyn serge@hallyn.com
• Tobias Klauser tklauser@distanz.ch
• Tycho Andersen tycho@tycho.ws
• W. Trevor King wking@tremily.us

Signed-off-by: Aleksa Sarai asarai@suse.de