subrepo: be more careful with deletions of .hgsub and .hgsubstate (
issue2844)
We shouldn't try to process subrepos if .hgsub isn't present and we
should remove .hgsubstate if .hgsub is marked for removal.
$ echo '[Section]' >> $HGRCPATH
$ echo 'KeY = Case Sensitive' >> $HGRCPATH
$ echo 'key = lower case' >> $HGRCPATH
$ hg showconfig Section
Section.KeY=Case Sensitive
Section.key=lower case