Add an implementation of the metadata store using kopia snapshots and restores to manage persistence of walk metadata. Metadata are stored to and retrieved from the store, and a mechanism for persisting the store is implemented using kopia snapshots.
Snapshotter interface describes an entity that can create,
restore, and delete snapshots, as well as manage a repository.
Add kopia implementation of the snapshotter interface.
Add comparer interface which gathers data on a path and
compares that data to a new path, returning error if the path
differs in any way from the input data. The details of what
constitutes a difference is left to the implementation.
FSWalker implementation uses Walk and Report to do the data
gathering and comparison. Filters are applied to sort out any
differences that might be expected (e.g. ctime, atime, mtime,
rename of root directory after restore).
