/static/style.css was served public, max-age=86400, must-revalidate
at an unversioned URL. must-revalidate only forces a check once
freshness expires, so for a day after a deploy a browser rendered the
new markup against its old stylesheet and the ETag from #132 was never
consulted.
Seen on a phone minutes after v1.31.0 deployed: the cached sheet
predated !440, so .railopt, .railmore and .raildrop had no rules.
Every rail icon showed instead of collapsing to five, the More menu
appeared at a width that hides it, and its drop rendered as a line of
inline links across the rail.
The hash that was already the ETag is split out as stylesheetHash and
exported to the template layer as web.StyleVersion, which the layout
stamps on the link as ?v=. A deploy changes the URL, so a cached copy
cannot answer it. A request carrying the current hash names bytes that
cannot change and is served max-age=31536000, immutable, dropping the
revalidation round trip; the bare URL keeps the policy it had.
TestStylesheetURLCarriesTheBuildHash renders a page and asserts the
link carries the hash, then checks both cache policies. It fails without
the layout change.
Closes #239