_restore_auto_maintenance unset any local maintenance.auto=false, so an
operator's own setting on a partial-clone checkout was erased on every
update (nothing records who wrote it). Remove it only with the first cut's
fingerprint: maintenance.auto, gc.writeCommitGraph and fetch.writeCommitGraph
all false and maintenance.commit-graph.enabled not yet set. The first pass
of disable_tree0_auto_maintenance writes that key, so the migration runs once
and an operator's setting is left alone before and after.
Review point from @Godhet on #131718.
ddebc788f2