The ping wrapper only asked whether the *target* had an AAAA record, never
whether this machine could reach over IPv6, so `ping ya.ru` ran ping6 and
died with "No route to host" while IPv4 worked fine.
Checking for a default v6 route is not sufficient either: this Mac has one
while holding only ::1 and fe80:: link-locals. So require a global unicast
address (2000::/3) as well as the route, which is the condition that
actually fails here.
ping4 is now platform-split rather than branching internally, since macOS
ping rejects -4:
macOS ~/.local/bin/ping (wrapper) and ~/.local/bin/ping4 -> /sbin/ping
Linux a fish function running `ping -4`
.chezmoiignore gates each side so neither lands where it cannot work.
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