backout of
d04ba50e104d: allow to qpop/push with a dirty working copy
The new behavior was breaking existing tools that relied on a sequence such as
this:
1) start with a dirty working copy
2) qimport some patch
3) try to qpush it
4) old behavior would fail at this point due to outstanding changes.
(new behavior would only fail if the outstanding changes and the patches
changes intersect)
5) innocent user qrefreshes, gets his local changes in the imported patch
It's worth considering if we can move this behavior to -f in the future.