This allows specifying the version to use in order to get
reproducible builds. The default is to use the max supported
version.

Signed-off-by: Alexander Larsson <[email protected]>

Linux upstream is making some change to how xwhiteout directories
are marked. They are now marked with an opaque xattr with content "x".

See:
 https://lore.kernel.org/linux-unionfs/CAOQ4uxh5x_-1j8HViCutVkghA1Uh-va+kJshCuvB+ep7WjmOFg@mail.gmail.com/T/#t

This creates a new image format version, 1, which adds these xattrs
(and the old ones for backwards compat with linux 6.7).

In addition, the tests are updated to handle this, and we create a new testcase that validates both v0 and v1 keeps working for whiteout files.

Note: This changes the output of the CLI tools to use the new version
by default, and you need to pass --verison-format=0 to get the old
version. This is ok at this point, as most images are unaffected by
the version due to lack of whiteouts, and not many people use
composefs yet.

Signed-off-by: Alexander Larsson <[email protected]>

… it back

Signed-off-by: Alexander Larsson <[email protected]>

Instead of specifying just the version we now specify the min and max
version, and composefs tries to keep the version as low as possible
but may bump it if needed for newer features. This is necessary as we
now record the version in the image, and we want to avoid
unnecessarily storing a later version in the image, as would change
the digest of images where this is not needed.

We also introduce new macros for the default max version to use in the
tooling, instead of just using the max version. This allows more
careful bumping of the default later.

Signed-off-by: Alexander Larsson <[email protected]>