tag/TagBuilder: overload Commit() returning a Tag object

src/decoder/FlacCommon.cxx

@@ -103,8 +103,8 @@ void flac_metadata_common_cb(const FLAC__StreamMetadata * block,
 
 		decoder_mixramp(data->decoder, flac_parse_mixramp(block));
 
-		flac_vorbis_comments_to_tag(data->tag,
-					    &block->data.vorbis_comment);
+		data->tag = flac_vorbis_comments_to_tag(&block->data.vorbis_comment);
+		break;
 
 	default:
 		break;

src/decoder/FlacMetadata.cxx

@@ -24,6 +24,7 @@
 #include "tag/TagHandler.hxx"
 #include "tag/TagTable.hxx"
 #include "tag/TagBuilder.hxx"
+#include "tag/Tag.hxx"
 #include "ReplayGainInfo.hxx"
 #include "util/ASCII.hxx"
 #include "util/SplitString.hxx"
@@ -199,13 +200,12 @@ flac_scan_metadata(const FLAC__StreamMetadata *block,
 	}
 }
 
-void
-flac_vorbis_comments_to_tag(Tag &tag,
-			    const FLAC__StreamMetadata_VorbisComment *comment)
+Tag
+flac_vorbis_comments_to_tag(const FLAC__StreamMetadata_VorbisComment *comment)
 {
 	TagBuilder tag_builder;
 	flac_scan_comments(comment, &add_tag_handler, &tag_builder);
-	tag_builder.Commit(tag);
+	return tag_builder.Commit();
 }
 
 void

src/decoder/FlacMetadata.hxx

@@ -130,9 +130,8 @@ flac_parse_replay_gain(ReplayGainInfo &rgi,
 MixRampInfo
 flac_parse_mixramp(const FLAC__StreamMetadata *block);
 
-void
-flac_vorbis_comments_to_tag(Tag &tag,
-			    const FLAC__StreamMetadata_VorbisComment *comment);
+Tag
+flac_vorbis_comments_to_tag(const FLAC__StreamMetadata_VorbisComment *comment);
 
 void
 flac_scan_metadata(const FLAC__StreamMetadata *block,

src/decoder/OpusDecoderPlugin.cxx

@@ -292,8 +292,7 @@ MPDOpusDecoder::HandleTags(const ogg_packet &packet)
 	    !tag_builder.IsEmpty()) {
 		decoder_replay_gain(decoder, &rgi);
 
-		Tag tag;
-		tag_builder.Commit(tag);
+		Tag tag = tag_builder.Commit();
 		cmd = decoder_tag(decoder, input_stream, std::move(tag));
 	} else
 		cmd = decoder_get_command(decoder);

src/input/CurlInputPlugin.cxx

@@ -782,7 +782,7 @@ copy_icy_tag(struct input_curl *c)
 	if (!c->meta_name.empty() && !tag->HasType(TAG_NAME)) {
 		TagBuilder tag_builder(std::move(*tag));
 		tag_builder.AddItem(TAG_NAME, c->meta_name.c_str());
-		tag_builder.Commit(*tag);
+		*tag = tag_builder.Commit();
 	}
 
 	c->tag = tag;

src/tag/TagBuilder.cxx

@@ -133,6 +133,14 @@ TagBuilder::Commit(Tag &tag)
 	Clear();
 }
 
+Tag
+TagBuilder::Commit()
+{
+	Tag tag;
+	Commit(tag);
+	return tag;
+}
+
 Tag *
 TagBuilder::CommitNew()
 {

src/tag/TagBuilder.hxx

@@ -97,6 +97,12 @@ public:
 	void Commit(Tag &tag);
 
 	/**
+	 * Create a new #Tag instance from data in this object.  This
+	 * object is empty afterwards.
+	 */
+	Tag Commit();
+
+	/**
 	 * Create a new #Tag instance from data in this object.  The
 	 * returned object is owned by the caller.  This object is
 	 * empty afterwards.