--slave alias remains but is undocumented, just for backward
compatibiltiy.

Use geohash limit defines in constraint check

CLI Help text loop verifies arg count

sentinel: fix randomized sentinelTimer.

bio: fix bioWaitStepOfType.

fix usage typo in redis-cli

See issue #5250 and issue #5292 for more info.

Here the idea is that we do not want freeMemoryIfNeeded() to propagate a
DEL command before the script and change what happens in the script
execution once it reaches the slave. For example see this potential
issue (in the words of @soloestoy):

On master, we run the following script:

    if redis.call('get','key')
    then
        redis.call('set','xxx','yyy')
    end
    redis.call('set','c','d')

Then when redis attempts to execute redis.call('set','xxx','yyy'), we call freeMemoryIfNeeded(), and the key may get deleted, and because redis.call('set','xxx','yyy') has already been executed on master, this script will be replicated to slave.

But the slave received "DEL key" before the script, and will ignore maxmemory, so after that master has xxx and c, slave has only one key c.

Note that this patch (and other related work) was authored collaboratively in
issue #5250 with the help of @soloestoy and @oranagra.

Related to issue #5250.

See issue #5250 and the new comments added to the code in this commit
for details.

Related to #5250.

See #5304.

networking: fix unexpected negative or zero readlen

The conclusion, that a xread request can be answered syncronously in
case that the stream's last_id is larger than the passed last-received-id
parameter, assumes, that there must be entries present, which could be
returned immediately.
This assumption fails for empty streams that actually contained some
entries which got removed by xdel, ... .

As result, the client is answered synchronously with an empty result,
instead of blocking for new entries to arrive.
An additional check for a non-empty stream is required.

Fix typo

networking: optimize parsing large bulk greater than 32k

fix multiple unblock for clientsArePaused()

Related to #5305.

If we are going to read a large object from network
try to make it likely that it will start at c->querybuf
boundary so that we can optimize object creation
avoiding a large copy of data.

But only when the data we have not parsed is less than
or equal to ll+2. If the data length is greater than
ll+2, trimming querybuf is just a waste of time, because
at this time the querybuf contains not only our bulk.

It's easy to reproduce the that:

Time1: call `client pause 10000` on slave.

Time2: redis-benchmark -t set -r 10000 -d 33000 -n 10000.

Then slave hung after 10 seconds.

Slight robustness improvement, especially if the limit values are
changed, as was suggested in antires/redis#4291 [1].

[1] https://github.com/antirez/redis/pull/4291

See #5297.

Technically speaking we don't really need to put the master client in
the clients that need to be processed, since in practice the PING
commands from the master will take care, however it is conceptually more
sane to do so.

Processing command from the master while the slave is in busy state is
not correct, however we cannot, also, just reply -BUSY to the
replication stream commands from the master. The correct solution is to
stop processing data from the master, but just accumulate the stream
into the buffers and resume the processing later.

Related to #5297.

However the master scripts will be impossible to kill.

Related to #5297.

See reasoning in #5297.

To avoid copying buffers to create a large Redis Object which
exceeding PROTO_IOBUF_LEN 32KB, we just read the remaining data
we need, which may less than PROTO_IOBUF_LEN. But the remaining
len may be zero, if the bulklen+2 equals sdslen(c->querybuf),
in client pause context.

For example:

Time1:

python
>>> import os, socket
>>> server="127.0.0.1"
>>> port=6379
>>> data1="*3\r\n$3\r\nset\r\n$1\r\na\r\n$33000\r\n"
>>> data2="".join("x" for _ in range(33000)) + "\r\n"
>>> data3="\n\n"
>>> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> s.settimeout(10)
>>> s.connect((server, port))
>>> s.send(data1)
28

Time2:

redis-cli client pause 10000

Time3:

>>> s.send(data2)
33002
>>> s.send(data3)
2
>>> s.send(data3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
socket.error: [Errno 104] Connection reset by peer

To fix that, we should check if remaining is greater than zero.

Revise the comments of latency command.

Correct "did not received" -> "did not receive" typos/grammar.

remove duplicate bind in sentinel.conf

Supplement to PR #4835, just take info/memory/command as random commands