doc: add the new init and getmanifest fields

doc/PLUGINS.md

@@ -85,7 +85,8 @@ this example:
 	"hooks": [
 		"openchannel",
 		"htlc_accepted"
-	]
+	],
+	"dynamic": true
 }
 ```
 
@@ -102,6 +103,10 @@ are mandatory, while the `long_description` can be omitted (it'll be
 set to `description` if it was not provided). `usage` should surround optional
 parameter names in `[]`.
 
+The `dynamic` indicates if the plugin can be managed after `lightningd`
+has been started. Critical plugins that should not be stop should set it
+to false.
+
 Plugins are free to register any `name` for their `rpcmethod` as long
 as the name was not previously registered. This includes both built-in
 methods, such as `help` and `getinfo`, as well as methods registered
@@ -122,7 +127,8 @@ simple JSON object containing the options:
 	},
 	"configuration": {
 		 "lightning-dir": "/home/user/.lightning",
-		 "rpc-file": "lightning-rpc"
+		 "rpc-file": "lightning-rpc",
+		 "startup": true
 	}
 }
 ```
@@ -132,6 +138,9 @@ arbitrary and will currently be discarded by `lightningd`. JSON-RPC
 commands were chosen over notifications in order not to force plugins
 to implement notifications which are not that well supported.
 
+The `startup` field allows a plugin to detect if it was started at
+`lightningd` startup (true), or at runtime (false).
+
 ## JSON-RPC passthrough
 
 Plugins may register their own JSON-RPC methods that are exposed

lightningd/plugin.c

@@ -69,6 +69,7 @@ void plugin_register(struct plugins *plugins, const char* path TAKES)
 	p->configured = false;
 	p->js_arr = tal_arr(p, struct json_stream *, 0);
 	p->used = 0;
+	p->signal_startup = false;
 
 	p->log = new_log(p, plugins->log_book, "plugin-%s",
 			 path_basename(tmpctx, p->cmd));
@@ -808,8 +809,10 @@ static void plugin_manifest_cb(const char *buffer,
 	}
 
 	dynamictok = json_get_member(buffer, resulttok, "dynamic");
-	if (dynamictok && json_to_bool(buffer, dynamictok, &dynamic_plugin))
+	if (dynamictok && json_to_bool(buffer, dynamictok, &dynamic_plugin)) {
+		plugin->signal_startup = true;
 		plugin->dynamic = dynamic_plugin;
+	}
 
 	if (!plugin_opts_add(plugin, buffer, resulttok) ||
 	    !plugin_rpcmethods_add(plugin, buffer, resulttok) ||

lightningd/plugin.h

@@ -23,6 +23,7 @@ struct plugin {
 	bool configured;
 	/* If this plugin can be restarted without restarting lightningd */
 	bool dynamic;
+	bool signal_startup;
 
 	/* Stuff we read */
 	char *buffer;