Returns a manifest whose newest epoch matches shards under hrw.
When the newest epoch already describes exactly this shard set with this
algorithm the manifest is returned unchanged, so this is safe to call on
every initialization. Otherwise a new epoch is prepended and every earlier
epoch is kept, because a key may still sit where only that epoch would look.
Returns a manifest whose newest epoch matches
shardsunderhrw.When the newest epoch already describes exactly this shard set with this algorithm the manifest is returned unchanged, so this is safe to call on every initialization. Otherwise a new epoch is prepended and every earlier epoch is kept, because a key may still sit where only that epoch would look.