# settings.json migrations

`settings.json` carries a top-level `"version"` (absent means 0). When a
release changes what settings.json may contain (a renamed or removed option, a
new default that must be written down), add `N.jq` here, where N is the next
number after the highest one. The file is a jq program that turns a version
N-1 document into a version N document; keep unknown keys as they are.

`router-update` runs the missing ones, in order, on the router's settings.json
before it rebuilds, and sets `"version"` after each. A release's schema version
is the number of `N.jq` files; the build refuses settings that are not at that
version, so a router never builds settings its release does not understand.

Example `1.jq`, renaming `router.wan.interface` to `router.wan.device`:

    .router.wan |= (.device = .interface | del(.interface))