player: make --shuffle/--merge-files affect runtime loaded playlists

Until now, these options took effect only at program start. This could
be confusing when e.g. doing "mpv list.m3u --shuffle". Make them always
take effect when a playlist is loaded either via a playlist file, or
with the "loadlist" command.

DOCS/man/options.rst

@@ -360,10 +360,6 @@ Program Behavior
     file. This uses timeline/EDL support internally. Note that this won't work
     for ordered chapter files.
 
-    This option is interpreted at program start, and doesn't affect for
-    example files or playlists loaded with the ``loadfile`` or ``loadlist``
-    commands.
-
 ``--no-resume-playback``
     Do not restore playback position from the ``watch_later`` configuration
     subdirectory (usually ``~/.config/mpv/watch_later/``).

player/command.c

@@ -4259,16 +4259,16 @@ int run_command(MPContext *mpctx, mp_cmd_t *cmd)
         bool append = cmd->args[1].v.i;
         struct playlist *pl = playlist_parse_file(filename, mpctx->global);
         if (pl) {
+            prepare_playlist(mpctx, pl);
+            struct playlist_entry *new = pl->current;
             if (!append)
                 playlist_clear(mpctx->playlist);
             playlist_append_entries(mpctx->playlist, pl);
             talloc_free(pl);
 
-            if (!append && mpctx->playlist->first) {
-                struct playlist_entry *e =
-                    mp_check_playlist_resume(mpctx, mpctx->playlist);
-                mp_set_playlist_entry(mpctx, e ? e : mpctx->playlist->first);
-            }
+            if (!append && mpctx->playlist->first)
+                mp_set_playlist_entry(mpctx, new ? new : mpctx->playlist->first);
+
             mp_notify_property(mpctx, "playlist");
         } else {
             MP_ERR(mpctx, "Unable to load playlist %s.\n", filename);

player/core.h

@@ -390,6 +390,7 @@ void mp_set_playlist_entry(struct MPContext *mpctx, struct playlist_entry *e);
 void mp_play_files(struct MPContext *mpctx);
 void update_demuxer_properties(struct MPContext *mpctx);
 void reselect_demux_streams(struct MPContext *mpctx);
+void prepare_playlist(struct MPContext *mpctx, struct playlist *pl);
 
 // main.c
 int mpv_main(int argc, char *argv[]);

player/loadfile.c

@@ -721,12 +721,30 @@ struct track *mp_add_subtitles(struct MPContext *mpctx, char *filename)
                               STREAM_SUB);
 }
 
+// Do stuff to a newly loaded playlist. This includes any processing that may
+// be required after loading a playlist.
+void prepare_playlist(struct MPContext *mpctx, struct playlist *pl)
+{
+    struct MPOpts *opts = mpctx->opts;
+
+    if (opts->shuffle)
+        playlist_shuffle(pl);
+
+    if (opts->merge_files)
+        merge_playlist_files(pl);
+
+    pl->current = mp_check_playlist_resume(mpctx, pl);
+    if (!pl->current)
+        pl->current = pl->first;
+}
+
 // Replace the current playlist entry with playlist contents. Moves the entries
 // from the given playlist pl, so the entries don't actually need to be copied.
 static void transfer_playlist(struct MPContext *mpctx, struct playlist *pl)
 {
     if (pl->first) {
-        struct playlist_entry *new = mp_check_playlist_resume(mpctx, pl);
+        prepare_playlist(mpctx, pl);
+        struct playlist_entry *new = pl->current;
         playlist_transfer_entries(mpctx->playlist, pl);
         // current entry is replaced
         if (mpctx->playlist->current)

player/main.c

@@ -457,15 +457,7 @@ int mp_initialize(struct MPContext *mpctx)
     mpctx->ipc_ctx = mp_init_ipc(mpctx->clients, mpctx->global);
 #endif
 
-    if (opts->shuffle)
-        playlist_shuffle(mpctx->playlist);
-
-    if (opts->merge_files)
-        merge_playlist_files(mpctx->playlist);
-
-    mpctx->playlist->current = mp_check_playlist_resume(mpctx, mpctx->playlist);
-    if (!mpctx->playlist->current)
-        mpctx->playlist->current = mpctx->playlist->first;
+    prepare_playlist(mpctx, mpctx->playlist);
 
     MP_STATS(mpctx, "end init");