Phabricator can't cope with text files that are not UTF-8, so requires them to
be submitted as binary files instead. This has the unfortunate effect of
making them practically unreviewable in Phabricator since it will only display
the separate versions of the file in other views, not a diff. phabreading
such submissions are similar, since it will just output the binary patch, but
hg import copes with it fine and hg diff afterwards will show the actual
changes. It is still a marked improvement over trying to submit them as text,
which just leads to corruption (Phabricator will either output ? or HTML
entities for non-UTF-8 characters, depending on context).
Running decode on the whole file like this seems slightly unfortunate, but I'm
not aware of a better way.
Needs to be done to p1() version as well to detect conversions to UTF-8.