fix: again allow formatting the working copy while merging
I forgot about unfinished merges (I think I was thinking only about
unfinished merge conflicts) when I wrote
https://phab.mercurial-scm.org/D11209. As a coworker (hg contributor
dploch) reported to me, this led to `hg fix --working-dir` failing
when you have an uncommitted merge. The fix is trivial: just move the
assertion to just before the call to `scmutil.movedirstate()` where it
actually matters.
Differential Revision: https://phab.mercurial-scm.org/D11376
$ hg init
$ echo a > a
$ hg ci -Am t
adding a
$ hg mv a b
$ hg ci -Am t1
$ hg debugrename b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3
$ hg mv b a
$ hg ci -Am t2
$ hg debugrename a
a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980
$ hg debugrename --rev 1 b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3