add a read-only variant for HELLO As discussed in https://github.com/antirez/redis/issues/7364, it is good to have a HELLO command variant, which does not switch the current proto version of a redis server.
add a read-only variant for HELLO
As discussed in https://github.com/antirez/redis/issues/7364, it is good
to have a HELLO command variant, which does not switch the current proto
version of a redis server.

While `HELLO` will work, it introduced a certain difficulty on parsing
options of the command. We will need to offset the index of authentication
and setname option by -1.

So 0 is marked a special version meaning non-switching. And we do not
need to change the code much.

ctripcorp/redis,charsyam/redis,oranagra/redis,PKRoma/redis,oranagra/redis,antirez/redis,yossigo/redis,yossigo/redis,neomantra/redis,PKRoma/redis,ctripcorp/redis,yossigo/redis,ofirluzon/redis,soloestoy/redis,neomantra/redis,charsyam/redis,antirez/redis,charsyam/redis,yossigo/redis,oranagra/redis,ofirluzon/redis,antirez/redis,antirez/redis,soloestoy/redis,PKRoma/redis,neomantra/redis,soloestoy/redis,charsyam/redis,ctripcorp/redis,ofirluzon/redis,PKRoma/redis,PKRoma/redis,yossigo/redis,charsyam/redis,ctripcorp/redis,soloestoy/redis,oranagra/redis,ofirluzon/redis,oranagra/redis,soloestoy/redis,neomantra/redis,ofirluzon/redis,neomantra/redis