Code review comment for lp:~songofacandy/bzr/fix-523746-2

> Perhaps dealing with this just for tempfiles is too much
> and sticking to ascii-only for the mangling is the best choice.

So I use ascii before.
But I find filename of tempfile is shown on GUI Diff title.
"old/????/????.txt - new/????/????.txt" isn't cool.