fn projection_key(
launch: &LegacyLaunch,
by_id: &HashMap<String, &LegacyLaunch>,
is_seeded: &HashMap<String, i64>,
) -> StringExpand description
Frozen copy of the v29 projection rule (see m0025’s own copy): walk
parent_instance_id to the chain root; if the root’s definition is a
user clone (is_seeded = 0) the key is that definition’s id, otherwise
it is the root launch’s own id. A missing definition counts as seeded.