The reason for this change is to support the upcoming redis-cluster since
it has different behaviors compared to the client-side cluster implementation
provided by Predis. For example redis-cluster will not support key tags or
certain operations currently available with our client-side implementation.
Now Predis\Command\ScriptedCommand uses EVALSHA instead of EVAL internally
so that performances should be better since the client do not resend the
Lua script body on each call.
Plain EVALSHA commands are not affected and will return or throw the error.
With a negative number Predis will count from the end of the arguments list
to calculate the actual number of keys that will be interpreted as elements
for `KEYS` by the underlying `EVAL` command.
Daniele Alessandri