Have convert use the new format when deciding path

By overriding the format attribute of the item, beets comes up with a
destination path that the user expects.

Author: j9ac9k

beetsplug/convert.py

@@ -355,6 +355,7 @@ def convert_item(
         item, original, converted = None, None, None
         while True:
             item = yield (item, original, converted)
+            item.format = fmt.upper()
             dest = item.destination(basedir=dest_dir, path_formats=path_formats)
 
             # Ensure that desired item is readable before processing it. Needed

docs/changelog.rst

@@ -30,6 +30,9 @@ Bug fixes:
 
 - |BeetsPlugin|: load the last plugin class defined in the plugin namespace.
   :bug:`6093`
+- Fixed convert plugin not taking into account the new format when determining
+  the target path.
+  :bug:`1360`
 
 For packagers: