rebase: add --confirm option This feature adds a functionality in rebase to confirm before applying changes. When there is no conflict and user confirm to apply actions, we just finish the unfinished rebase. But when there is a conflict and user confirm to apply actions then we can't just finish rebasing using rbsrt._finishrebase() because in-memory merge doesn't support conflicts, so we have to abort and run on-disk merge in this case. And if user doesn't confirm to apply actions then simply abort the rebase. Differential Revision: https://phab.mercurial-scm.org/D3870

revlog: introduce a isancestorrev() and use it in rebase Differential Revision: https://phab.mercurial-scm.org/D3931

revlog: make isdescendantrev(a, b) check if a < b This check was taken from rebase.py. It seems to make sense to move it here, but I haven't done any measurements. Differential Revision: https://phab.mercurial-scm.org/D3930

revlog: replace descendant(b, a) by isdescendantrev(a, b) (API) The "is" is to match "isancestor" and to make it clear that it doesn't return a descendant. The "rev" is to make it clear that it's not about nodeids (unlike e.g. isancestor()). The argument order change is just seems more natural (and makes isancestor() less confusing). Differential Revision: https://phab.mercurial-scm.org/D3929

revlog: move comment about commonancestorsheads where it's used Differential Revision: https://phab.mercurial-scm.org/D3928

removeemptydirs: add test for `hg split` inside a disappearing directory Differential Revision: https://phab.mercurial-scm.org/D3927