Code review comment for lp:~mbp/bzr/456077-cross-format-fetch

On IRC Martin asked me to look at the UIFactory changes, i.e. the new show_user_warning/suppressed_warnings API. It looks fine to me. I like the paranoia when looking up the warning string and trying to format it. I think the API to temporarily suppress a particular warning is a bit cumbersome, but good enough for now (perhaps we'll think of improvements later if we use it more heavily). So, for that aspect of the patch, +1.

I haven't yet really looked at the part of the patch that emits warnings about slow fetches, although removing code from bzrlib/smart is a promising sign :)