[PATCH] blackbox: add an option to customize the name of the log file

[Jun Wu]

Excerpts from Yuya Nishihara's message of 2016-06-16 22:55:45 +0900:
> It seems confusing that filesuffix isn't a suffix. Is there a reason to
> not allow specifying the full file name? Invalid path components such as
> '..' will be rejected by pathauditor.

I'd like to have flexible full names as well.

My main concern is names like "requires", "dirstate", "hgrc" are dangerous.
But if we move them to ".hg/blackbox" and disallow "/", then everything will
be fine.

If putting everything under "blackbox" subdirectory (including blackbox.log)
makes sense, I can prepare the patch. If compatibilities are a concern, I
can symlink blackbox.log.

> Perhaps it would be better to report error than stripping bad characters
> silently.

Good idea.