tests: remove some tests which are moved to dedicated files The tests in test-unstable.t files are now moved to their dedicated file with all the cases to that in that file. Let's delete them from here.

next: factor out the logic to update to changeset in another function This patch moves the logic to update to children changeset during `hg next` in a separate function because we want to re-use the logic when we will prompt user to choose a changeset in case of multiple childrens.

utility: add a function to prompt user to choose a revision This patch adds a utility function to interactively prompt user to choose a revision to proceed in cases when there are multiple revisions which are candidates. The function will be used in `hg evolve`, `hg next`, `hg prev` etc. If user feedback will be good, I plan to move it to core and use it at more possible places.

tests: add a test about evolve stabilizing orphan caused by splits There are some similar tests lying around in the test suite but they are not well arranged. I wanted the test suite to be a goto reference for all the behaviors till the time we get all of them documented.

test: fix output after rev-branch-cache has been merged Mercurial core 2090044a288d added a new revbranchcache part which changed some exchange-related outputs. Glob them to ease merging with old Mercurial versions branches.

cleanup: remove duplicate import of "obsolete"

previous: fix behavior on obsolete cset when topic is involved (issue5708) This patch fixes the behavior of `hg previous` when done on an obsolete changeset having a successor of different topic. The underlying code is bit messed up, I wanted to split the topic handling to topic extension but I have postponed it to next bug.