fn parse_dir_name(name: &str) -> Option<(i64, i64, u32, u64, u64)>Expand description
Parses both the five-field name above and the four-field name that predates the write-ahead log.
The old form has to keep working: a block directory written by an earlier
build is still a valid block, and there is no migration step to run because
there is no metadata store to migrate. A missing wal_hi reads as 0,
which is correct — those blocks came from a Mira with no log, so no
sequence is covered by them and replay must not skip anything on their
account.