This is part of a patchset that refactors all of the checking logic into
comparison operations. Essentially, provide a Compare(...) function that
allows for two different manifests to be compared. Extra and missing
entries are supported in addition to the standard modified entry, and by
implementing as a manifest comparison there is no double-scanning of the
manifest source.
The main annoyance is that we have to also include tar_time handling,
which has not been abstracted inside keywords.go. This is a bit ugly
right now, but works fine for the moment.
Signed-off-by: Aleksa Sarai <asarai@suse.de>