StorageCommands: emit IDLE_MOUNT on successful "mount"

Add the new idle event to Idle.hxx/Idle.cxx.

src/Idle.cxx

@@ -46,6 +46,7 @@ static const char *const idle_names[] = {
 	"subscription",
 	"message",
 	"neighbor",
+	"mount",
 	nullptr
 };
 

src/Idle.hxx

@@ -64,6 +64,9 @@ static constexpr unsigned IDLE_MESSAGE = 0x400;
 /** a neighbor was found or lost */
 static constexpr unsigned IDLE_NEIGHBOR = 0x800;
 
+/** the mount list has changed */
+static constexpr unsigned IDLE_MOUNT = 0x1000;
+
 /**
  * Adds idle flag (with bitwise "or") and queues notifications to all
  * clients.

src/command/StorageCommands.cxx

@@ -29,6 +29,7 @@
 #include "Instance.hxx"
 #include "storage/Registry.hxx"
 #include "storage/CompositeStorage.hxx"
+#include "Idle.hxx"
 
 static void
 print_storage_uri(Client &client, const Storage &storage)
@@ -109,5 +110,6 @@ handle_mount(Client &client, gcc_unused int argc, char *argv[])
 	}
 
 	composite.Mount(local_uri, storage);
+	idle_add(IDLE_MOUNT);
 	return CommandResult::OK;
 }