db/simple/Song: rename "uri" to "filename"

This attribute is not a URI; it is just the filename without its
parent directory path.  To avoid confusion, let's rename it to
"filename", leaving the struct without a "uri" attribute.

src/db/plugins/simple/Directory.cxx

@@ -191,7 +191,7 @@ Directory::FindSong(const char *name_utf8) const noexcept
 	for (auto &song : songs) {
 		assert(&song.parent == this);
 
-		if (song.uri == name_utf8)
+		if (song.filename == name_utf8)
 			return &song;
 	}
 

src/db/plugins/simple/Song.cxx

@@ -30,7 +30,7 @@ Song::Song(DetachedSong &&other, Directory &_parent) noexcept
 	 mtime(other.GetLastModified()),
 	 start_time(other.GetStartTime()),
 	 end_time(other.GetEndTime()),
-	 uri(other.GetURI())
+	 filename(other.GetURI())
 {
 }
 
@@ -38,17 +38,17 @@ std::string
 Song::GetURI() const noexcept
 {
 	if (parent.IsRoot())
-		return uri;
+		return filename;
 	else {
 		const char *path = parent.GetPath();
-		return PathTraitsUTF8::Build(path, uri.c_str());
+		return PathTraitsUTF8::Build(path, filename.c_str());
 	}
 }
 
 LightSong
 Song::Export() const noexcept
 {
-	LightSong dest(uri.c_str(), tag);
+	LightSong dest(filename.c_str(), tag);
 	if (!parent.IsRoot())
 		dest.directory = parent.GetPath();
 	dest.mtime = mtime;

src/db/plugins/simple/Song.hxx

@@ -91,11 +91,11 @@ struct Song {
 	/**
 	 * The file name.
 	 */
-	std::string uri;
+	std::string filename;
 
-	template<typename U>
-	Song(U &&_uri, Directory &_parent) noexcept
-		:parent(_parent), uri(std::forward<U>(_uri)) {}
+	template<typename F>
+	Song(F &&_filename, Directory &_parent) noexcept
+		:parent(_parent), filename(std::forward<F>(_filename)) {}
 
 	Song(DetachedSong &&other, Directory &_parent) noexcept;
 

src/db/plugins/simple/SongSort.cxx

@@ -96,7 +96,7 @@ song_cmp(const Song &a, const Song &b) noexcept
 		return ret < 0;
 
 	/* still no difference?  compare file name */
-	return IcuCollate(a.uri.c_str(), b.uri.c_str()) < 0;
+	return IcuCollate(a.filename.c_str(), b.filename.c_str()) < 0;
 }
 
 void