rhg: Make Repo::dirstate_parents a LazyCell
Unify with the same abstraction used for other lazily-initialized components
Differential Revision: https://phab.mercurial-scm.org/D11837
$ cat >> $HGRCPATH << EOF
> [extensions]
> absorb=
> drawdag=$TESTDIR/drawdag.py
> EOF
$ hg init
$ hg debugdrawdag <<'EOS'
> C
> |
> B
> |
> A
> EOS
$ hg phase -r A --public -q
$ hg phase -r C --secret --force -q
$ hg update C -q
$ printf B1 > B
$ hg absorb -aq
$ hg log -G -T '{desc} {phase}'
@ C secret
|
o B draft
|
o A public