the snapshot string format is not backwards compatible since it now has
an in-line namespace prefix. it's possible to select which magic to use
at the start of the backup, since a tape backup job knows whether it
operates on non-root namespaces up-front.
the MediaCatalog itself also has a similar incompatible change, but
there
- updating existing catalogs in-place
- not knowing what the catalog will contain in the future when initially
creating/opening it
makes bumping the magic there harder. since the tape contents are
sufficiently guarded by the other two bumps, ignoring the
backwards-incomaptible change of the on-disk catalogs seems like an okay
tradeoff.
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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