The service worker answers app routes from its kept page (#395), and it
kept whatever the mount's root returned at install and whatever HTML a
navigation returned. Where the root is not the app -- demo.ihasmail.com
puts its landing page there -- a returning visitor got the landing page on
every route.
The kept page is now only ever the app page, recognised by the asset list
the build writes into it: install fetches /mail instead of /, a
navigation's page is kept only if it is the app's, and a foreign page left
by the earlier worker is dropped when this one activates. Only the app's
own routes are answered from it; the root and any page in front of the app
go to the network. The reload for a new build primes the kept page from
/mail for the same reason.
jcoffey
2740129c6a