command/playlist: "load" supports relative positions

This commit also increases the PROTOCOL_VERSION so clients can detect
the availability of the feature.

NEWS

@@ -1,6 +1,7 @@
 ver 0.23.1 (not yet released)
 * protocol
   - use decimal notation instead of scientific notation
+  - "load" supports relative positions
 * output
   - pipewire: attempt to change the graph sample rate
   - snapcast: fix time stamp bug which caused "Failed to get chunk"

doc/protocol.rst

@@ -923,8 +923,9 @@ remote playlists (absolute URI with a supported scheme).
     only a part of the playlist.
 
     The ``POSITION`` parameter specifies where the songs will be
-    inserted into the queue.  (This requires specifying the range as
-    well; the special value `0:` can be used if the whole playlist
+    inserted into the queue; it can be relative as described in
+    :ref:`addid <command_addid>`.  (This requires specifying the range
+    as well; the special value `0:` can be used if the whole playlist
     shall be loaded at a certain queue position.)
 
 .. _command_playlistadd:

meson.build

@@ -44,7 +44,7 @@ version_conf = configuration_data()
 version_conf.set_quoted('PACKAGE', meson.project_name())
 version_conf.set_quoted('PACKAGE_NAME', meson.project_name())
 version_conf.set_quoted('VERSION', meson.project_version())
-version_conf.set_quoted('PROTOCOL_VERSION', '0.23.0')
+version_conf.set_quoted('PROTOCOL_VERSION', '0.23.1')
 configure_file(output: 'Version.h', configuration: version_conf)
 
 conf = configuration_data()

src/command/PlaylistCommands.cxx

@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "PlaylistCommands.hxx"
+#include "PositionArg.hxx"
 #include "Request.hxx"
 #include "Instance.hxx"
 #include "db/Selection.hxx"
@@ -86,7 +87,7 @@ handle_load(Client &client, Request args, [[maybe_unused]] Response &r)
 	const unsigned old_size = playlist.GetLength();
 
 	const unsigned position = args.size > 2
-		? args.ParseUnsigned(2, old_size)
+		? ParseInsertPosition(args[2], partition.playlist)
 		: old_size;
 
 	const SongLoader loader(client);