refactor(emqx_conf_cli): rename cluster_call ctl command

Renamed 'clustedr_call' ctl command to 'cluster_sync' as a sub-command
of 'conf'
The old 'cluster_call' command is kept, but no usage prints

apps/emqx_conf/src/emqx_conf_cli.erl

@@ -22,11 +22,12 @@
     unload/0
 ]).
 
+%% kept cluster_call for compatibility
 -define(CLUSTER_CALL, cluster_call).
 -define(CONF, conf).
 
 load() ->
-    emqx_ctl:register_command(?CLUSTER_CALL, {?MODULE, admins}, []),
+    emqx_ctl:register_command(?CLUSTER_CALL, {?MODULE, admins}, [hidden]),
     emqx_ctl:register_command(?CONF, {?MODULE, conf}, []).
 
 unload() ->
@@ -41,17 +42,10 @@ conf(["show", Key]) ->
     print_hocon(get_config(Key));
 conf(["load", Path]) ->
     load_config(Path);
+conf(["cluster_sync" | Args]) ->
+    admins(Args);
 conf(_) ->
-    emqx_ctl:usage(
-        [
-            %% TODO add reload
-            %{"conf reload", "reload etc/emqx.conf on local node"},
-            {"conf show --keys-only", "print all keys"},
-            {"conf show", "print all running configures"},
-            {"conf show <key>", "print a specific configuration"},
-            {"conf load <path>", "load a hocon file to all nodes"}
-        ]
-    ).
+    emqx_ctl:usage(usage_conf() ++ usage_sync()).
 
 admins(["status"]) ->
     status();
@@ -87,14 +81,33 @@ admins(["fast_forward", Node0, ToTnxId]) ->
     emqx_cluster_rpc:fast_forward_to_commit(Node, TnxId),
     status();
 admins(_) ->
-    emqx_ctl:usage(
-        [
-            {"cluster_call status", "status"},
-            {"cluster_call skip [node]", "increase one commit on specific node"},
-            {"cluster_call tnxid <TnxId>", "get detailed about TnxId"},
-            {"cluster_call fast_forward [node] [tnx_id]", "fast forwards to tnx_id"}
-        ]
-    ).
+    emqx_ctl:usage(usage_sync()).
+
+usage_conf() ->
+    [
+        %% TODO add reload
+        %{"conf reload", "reload etc/emqx.conf on local node"},
+        {"conf show --keys-only", "Print all config keys"},
+        {"conf show", "Print config in use"},
+        {"conf show <key>", "Print configs under the given key"},
+        {"conf load <path>",
+            "Load a HOCON format config file."
+            "The config is overlay on top of the existing configs. "
+            "The current node will initiate a cluster wide config change "
+            "transaction to sync the changes to other nodes in the cluster. "
+            "NOTE: do not make runtime config changes during rolling upgrade."}
+    ].
+
+usage_sync() ->
+    [
+        {"conf cluster_sync tatus", "Show cluster config sync status summary"},
+        {"conf cluster_sync skip [node]", "Increase one commit on specific node"},
+        {"conf cluster_sync tnxid <TnxId>",
+            "Display detailed information of the config change transaction at TnxId"},
+        {"conf cluster_sync fast_forward [node] [tnx_id]",
+            "Fast-forward config change transaction to tnx_id on the given node."
+        "WARNING: This results in inconsistent configs among the clustered nodes."}
+    ].
 
 status() ->
     emqx_ctl:print("-----------------------------------------------\n"),