Don't let "reopen_log" rotate files (EJAB-1243)

Make sure the "reopen_log" command really just reopens log files without
also rotating them.  For rotating log files, the new "rotate_log"
command can be used.

src/ejabberd_admin.erl

@@ -28,7 +28,7 @@
 
 -export([start/0, stop/0,
 	 %% Server
-	 status/0, reopen_log/0,
+	 status/0, reopen_log/0, rotate_log/0,
 	 set_loglevel/1,
 	 stop_kindly/2, send_service_message_all_mucs/2,
 	 registered_vhosts/0,
@@ -88,6 +88,10 @@ commands() ->
 			desc = "Reopen the log files",
 			module = ?MODULE, function = reopen_log,
 			args = [], result = {res, rescode}},
+     #ejabberd_commands{name = rotate_log, tags = [logs, server],
+			desc = "Rotate the log files",
+			module = ?MODULE, function = rotate_log,
+			args = [], result = {res, rescode}},
      #ejabberd_commands{name = stop_kindly, tags = [server],
 			desc = "Inform users and rooms, wait, and stop the server",
 			longdesc = "Provide the delay in seconds, and the "
@@ -276,6 +280,9 @@ reopen_log() ->
     ejabberd_hooks:run(reopen_log_hook, []),
     ejabberd_logger:reopen_log().
 
+rotate_log() ->
+    ejabberd_hooks:run(rotate_log_hook, []),
+    ejabberd_logger:rotate_log().
 
 set_loglevel(LogLevel) ->
     {module, Module} = ejabberd_logger:set(LogLevel),

src/ejabberd_logger.erl

@@ -27,7 +27,7 @@
 -behaviour(ejabberd_config).
 
 %% API
--export([start/0, reopen_log/0, get/0, set/1, get_log_path/0, opt_type/1]).
+-export([start/0, reopen_log/0, rotate_log/0, get/0, set/1, get_log_path/0, opt_type/1]).
 
 -include("ejabberd.hrl").
 
@@ -36,6 +36,7 @@
 -spec start() -> ok.
 -spec get_log_path() -> string().
 -spec reopen_log() -> ok.
+-spec rotate_log() -> ok.
 -spec get() -> {loglevel(), atom(), string()}.
 -spec set(loglevel() | {loglevel(), list()}) -> {module, module()}.
 
@@ -128,6 +129,10 @@ start() ->
     ok.
 
 reopen_log() ->
+    %% Lager detects external log rotation automatically.
+    ok.
+
+rotate_log() ->
     lager_crash_log ! rotate,
     lists:foreach(
       fun({lager_file_backend, File}) ->
@@ -191,6 +196,10 @@ reopen_log() ->
     p1_logger_h:reopen_log(),
     reopen_sasl_log().
 
+rotate_log() ->
+    %% Not implemented.
+    ok.
+
 get() ->
     p1_loglevel:get().