patch: use field names instead of field numbers on scmutil.status
As part of my pytype adventures I want to make scmutil.status no longer a
subclass of tuple. This is part of that process.
Differential Revision: https://phab.mercurial-scm.org/D7401
Set up
$ hg init repo
$ cd repo
Try to import an empty patch
$ hg import --no-commit - <<EOF
> EOF
applying patch from stdin
abort: stdin: no diffs found
[255]
No dirstate backups are left behind
$ ls .hg/dirstate* | sort
.hg/dirstate