Verify genuine Google music constraints and separate metadata cache revisions

README.md

@@ -39,6 +39,13 @@ sound.
 Use **All files** to narrow results by folder, file extension, modification
 date, file size or media duration. Choose a result to inspect it before opening.
 
+The current source also offers **Artist (exact)** and **Track title (exact)**
+filters for music. Enter the complete tag, with or without a text query. These
+filters ignore letter case and surrounding spaces; files without the matching
+music tag stay out of the results. Existing indexes need a media indexing pass
+before these new filters can use their tags. This improvement is not yet in the
+v0.1.4 downloads.
+
 ### Find the implementation
 
 Choose **Code** in the **All files** filters to search source files. Look up a