mdiff.diffopts: add a new noprefix option By popular demand, we introduce an option to disable the 'a/' and 'b/' prefixes in diff output. This makes copying and pasting filenames from diff output easier. This option will be implemented and documented in upcoming patches. To ensure that existing scripts that parse output don't break, we will ensure that this prefix is disabled in plain mode. A straight 'hg export | hg import' without HGPLAIN=1 will still be broken though, but there's little that can be done about that.