clarify --signal flag help

Signed-off-by: Alex Bozhenko <[email protected]>

Author: alexbozhenko

main.go

@@ -37,7 +37,13 @@ Server Options:
     -ms,--https_port <port>          Use port for https monitoring
     -c, --config <file>              Configuration file
     -t                               Test configuration and exit
-    -sl,--signal <signal>[=<pid>]    Send signal to nats-server process (ldm, stop, quit, term, reopen, reload)
+    -sl,--signal <command>[=<pid>]   Send signal to a running nats-server
+                                       ldm (SIGUSR2) - graceful shutdown (evicts clients gradually)
+                                       quit (SIGINT) - graceful shutdown
+                                       term (SIGTERM) - graceful shutdown
+                                       stop (SIGKILL) - immediate termination
+                                       reload (SIGHUP) - reload configuration
+                                       reopen (SIGUSR1) - reopen log files
                                      <pid> can be either a PID (e.g. 1) or the path to a PID file (e.g. /var/run/nats-server.pid)
         --client_advertise <string>  Client URL to advertise to other servers
         --ports_file_dir <dir>       Creates a ports file in the specified directory (<executable_name>_<pid>.ports).