evolve: store the base of content-divergents in evolvestate We need the base changeset for merging commit messages, branches. Let's store it in evolvestate.

evolve: use cmdrewrite.amend() instead of creating a new commit This patch backs out changeset 88601e1cd5d8. We replaced cmdrewrite.amend() with creating new commit because using amend(), a high level function was not good and creating a new commit gave us more control over things. **HOWEVER** to get more control, you need to get arrange all the pieces together perfectly. Creating a new commit, the existing logic has some bugs around dirstate handling, the `repo.dirstate.setparents()` call especially. Sometimes this fixes the dirstate correctly sometimes not. As Pierre-Yves David said, "Having a "clumsy" implementation with the right behavior is usually a good first step. So having an amend based implementation seems like a good first step.", let's take a step back and get back using amend so that we can have a correct basic implementation which is bug free.

corecompat: update the tests output to show phase update summary eb9835014d20 in core added support to transactions to show a summary on the phase changed during that transaction. Due to this, couple of tests output needs to be updated. This patch does that. While realeasing evolve, this patch should be backed out on branches where hg<=4.6. CORE-TEST-OUTPUT-UPDATE: eb9835014d20

CHANGELOG: add an entry about issue 5808 being fixed

next-prev: replace the error hint to mention about `--merge` flag

tests: add tests for conflicts while respecting commands.update.check This patch adds tests to check that we don't run into conflicts while respecting commands.update.check. The error message now does not show the hint about --merge option which we should fix.