convert: clear the dirstate before a conversion, invalidate it afterwards
Clearing it before the conversion protects us from whatever data were
there (file copies in particular).
Invalidating it after the conversion avoids writing a possibly
inconsistent dirstate to disk.
import doctest
import mercurial.changelog
# test doctest from changelog
doctest.testmod(mercurial.changelog)
import mercurial.httprepo
doctest.testmod(mercurial.httprepo)