[gexiv2] Improve _try_tag_supports_multiple_values() docs

[Jens Georg <jensgeorg src gnome org>]

commit 1463cfbc9e48acec70c6013450600fcee10f6b23
Author: postscript-dev <43813-postscript-dev users noreply gitlab gnome org>
Date:   Sat Mar 20 16:26:46 2021 +0000

    Improve _try_tag_supports_multiple_values() docs

 gexiv2/gexiv2-metadata.h | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/gexiv2/gexiv2-metadata.h b/gexiv2/gexiv2-metadata.h
index a247ec4..47e56f4 100644
--- a/gexiv2/gexiv2-metadata.h
+++ b/gexiv2/gexiv2-metadata.h
@@ -543,6 +543,10 @@ const gchar*       gexiv2_metadata_get_tag_type    (const gchar *tag);
  *
  * The Exiv2 Tag Reference can be found at <ulink url="https://www.exiv2.org/metadata.html";></ulink>
  *
+ * Multiple value tags are Xmp tags of type "XmpAlt", "XmpBag", "XmpSeq" or "LangAlt", or Iptc
+ * tags marked as Repeatable (which can be of any Iptc type). There are no multiple value Exif
+ * tags.
+ *
  * Returns: Whether @tag is capable of storing multiple values or not. If @tag is undefined
  * (i.e. not built-in and not added to @self), then @error is set and %FALSE is returned.
  *