We now ignore payloads where payload['push']['changes'] is empty,
because an empty push doesn't really convey any useful information.
I couldn't find a way to replicate the action that would generate
such a payload, so I took one of our existing payloads and editted
out payload['push']['changes'] myself, so this payload is not
authentic.
All webhook fixtures in zerver/fixtures/<webhook_name> have now
been moved to dedicated webhook-specific directories under
zerver/webhooks/<webhook_name>/fixtures, where <webhook_name> is
the name of the webhook.
Eeshan Garg