Comment 1 for bug 259928

I have re-written the substitution string code, and will have this resolved soon, I hope. The complication is that allowing variable expansion in else clauses opens up the possibility of ambiguous results from splitting paths. For instance, with a format string like:

%?%{artist}%:%{composer}%?

If we rename a file from "foo" to "bar", should that affect the artist or composer tag?

Here are the options:

 * Always affect the tag in the "if" clause.
 * Always affect the tag in the "else" clause.
 * Change the one that is currently being used. I.e., if the artist is "foo" and rename the file to "bar", set the artist tag to "bar". However, if the artist tag is not set but the composer is "foo", set the composer tag to "bar". This is obviously a little more difficult.
 * Set neither and throw back an error (Invalid argument, I guess).

I'm still contemplating which option is best. Input is always appreciated.