Feature request: add a function to query the xmp namespace of a tag
With the way we store metadata in GIMP we need a way to know the namespace of xmp tags in cases where they are not registered by exiv2 to be able to export xmp metadata including tags that use such a namespace.
If we had access to a function to query the xmp namespace (returning NULL if not found) we could store those namespaces and be more complete in the xmp metadata we can handle and export.
The main GIMP issue collecting the namespaces that we currently can't handle is here: gimp#5863 (closed), which is also the issue that started the GError changes in gexiv2.
I might have a look at implementing this but am currently deep into fixing GIMP bugs so it might be a while before I get around to it. If anyone else feels like taking a look at it that would be welcome