tests: add test of resolution of content-divergent stacks This patch adds a test of resolution of content-divergence stacks where a series of changesets get mutated as two different series resulting in whole content-divergent stacks. As the tests shows, we are not processing the changesets in right order which needs to be fixed first.

test-drop.t
test-inhibit.t
test-simple4server.t
tests/test-simple4server-bundle2.t