Changes touching this path

• an unexpected head stops being something the operator can only fold on faith, because `loot heads` lists every live head with what introduced it and how many changes it holds of its own — and since a head is a tip no other head reaches, a count of zero can only mean the head is not live, so #1477s empty head is superseded and the converge it asks for would merge nothing (#1496) 955ec9ff · dbf3dbe6…

Renames are not followed. loot's tree maps a path to an address, so a rename is a delete and an add. This list is the history of the name, not of the bytes.