master-server/deps/curl/docs/cmdline-opts/http2-prior-knowledge.md

c	SPDX-License-Identifier	Long	Tags	Protocols	Added	Mutexed	Requires	Help	Category	Multi	See-also	Example
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.	curl	http2-prior-knowledge	Versions	HTTP	7.49.0	http1.1 http1.0 http2 http3	HTTP/2	Use HTTP 2 without HTTP/1.1 Upgrade	http	boolean	http2 http3	--http2-prior-knowledge $URL

--http2-prior-knowledge

Issue a non-TLS HTTP requests using HTTP/2 directly without HTTP/1.1 Upgrade. It requires prior knowledge that the server supports HTTP/2 straight away. HTTPS requests still do HTTP/2 the standard way with negotiated protocol version in the TLS handshake.