EBML: Stub MergeTag impl

Author: Serial-ATA

lofty/src/ebml/tag/generic.rs

@@ -136,13 +136,13 @@ matroska_mapping_tables!(
 const TAG_RETAINED: bool = true;
 const TAG_CONSUMED: bool = false;
 
-pub(super) fn split_tag(mut ebml_tag: MatroskaTag) -> (MatroskaTag, Tag) {
+pub(super) fn split_tag(mut matroska_tag: MatroskaTag) -> (MatroskaTag, Tag) {
 	let mut tag = Tag::new(TagType::Matroska);
 
 	// TODO: Pictures, can they be handled in a generic way?
 	//       What about the uid and referral?
 
-	ebml_tag.tags.retain_mut(|t| {
+	matroska_tag.tags.retain_mut(|t| {
 		let target_type = match &t.target {
 			Some(t) if !t.has_uids() => t.target_type,
 			// We cannot use any tags bound to uids
@@ -159,7 +159,7 @@ pub(super) fn split_tag(mut ebml_tag: MatroskaTag) -> (MatroskaTag, Tag) {
 		return TAG_RETAINED;
 	});
 
-	(ebml_tag, tag)
+	(matroska_tag, tag)
 }
 
 fn split_simple_tags(
@@ -196,3 +196,7 @@ fn split_simple_tags(
 
 	return TAG_CONSUMED;
 }
+
+pub(super) fn merge_tag(tag: Tag, matroska_tag: MatroskaTag) -> MatroskaTag {
+	todo!()
+}

lofty/src/ebml/tag/mod.rs

@@ -367,8 +367,8 @@ impl SplitTag for MatroskaTag {
 impl MergeTag for SplitTagRemainder {
 	type Merged = MatroskaTag;
 
-	fn merge_tag(self, _tag: crate::tag::Tag) -> Self::Merged {
-		todo!()
+	fn merge_tag(self, tag: crate::tag::Tag) -> Self::Merged {
+		generic::merge_tag(tag, self.0)
 	}
 }
 
@@ -385,7 +385,13 @@ impl From<MatroskaTag> for crate::tag::Tag {
 }
 
 impl From<crate::tag::Tag> for MatroskaTag {
-	fn from(input: crate::tag::Tag) -> Self {
+	fn from(mut input: crate::tag::Tag) -> Self {
+		if unsafe { global_options().preserve_format_specific_items } {
+			if let Some(companion) = input.companion_tag.take().and_then(CompanionTag::matroska) {
+				return SplitTagRemainder(companion).merge_tag(input);
+			}
+		}
+
 		SplitTagRemainder::default().merge_tag(input)
 	}
 }