Comment 9 for bug 1262875

ok, but it does not work.
The initial request is to accept beside "catalog" also "catalogue" and "_catalog".
The match calibre/db/adding.py row 252 will find all of them which is perfect.

Your change in row 263/267 prevent "hardcoding" the catalog tag which is perfect too.

But your new else-statement in row 271 is a problem as mi_tag is NONE for existing books and therefore existing tags will be overwritten.

Please remove 271 and 272 and everything works as expected.
In case the user delete all tags or use something different to *catalog*, the match will not found it and a new catalog will be created instead of overwriting which is same as old behaviour.