Client disclaimer

[fungalcofe]

Hi,

I added a small feature to display a custom message/disclaimer when a user creates a tmate session.
When server is start with a -d flag and an associated string, the disclaimer is display just after the note:.
If no disclaimer is declared no print will be done.

Note

Escape characters such as \n will be print in the disclaimer and won't produce a line feed.

e.g.

server:

$ nocorrect docker run --rm -v /tmp/tma:/root/ -p 2200:2200 -e SSH_KEYS_PATH=/root --cap-add=SYS_ADMIN antonin/tmate-ssh-server -d "    -> Hello and Welcome to tmate \! <-"
sh: out of range
sh: out of range
Loading key /root/ssh_host_ed25519_key
Accepting connections on :2200
[LtxQ...] Spawning daemon ip=172.17.0.1
[LtxQ...] tmate version=2.4.0, protocol=6
[LtxQ...] sysname=Linux machine=x86_64 release=5.4.111 version=#1-NixOS SMP Sat Apr 10 11:34:32 UTC 2021 nodename=rilakkuma

client:

Tip: if you wish to use tmate only for remote access, run: tmate -F                                                                [0/0]
To see the following messages again, run in a tmate session: tmate show-messages
Press <q> or <ctrl-c> to continue
---------------------------------------------------------------------
Connecting to localhost...
Note: clear your terminal before sharing readonly access
    -> Hello and Welcome to tmate ! <-
ssh session read only: ssh -p2200 ro-PVWBWbhUQMgrTsEKJyzzM3dXy@35dea2f45857
ssh session: ssh -p2200 LtxQZV98ybg2YVwAxftcFhpp8@35dea2f45857