evolve: create a new commit instead of amending one of the divergents This patch changes the behavior of evolve command while resolving content-divergence to create a new commit instead of amending one of the divergent ones. In past, I have made this change, backed out this change and now today again I am doing this change, so let's dive in some history. Using cmdrewrite.amend() was never a good option as that requires hack to delete the evolvestate and also gives us less control over things. We can't make the commit on top of different parents as that of content-divergent ones. Due to all these, I first made this change to create a new commit instead of amending one. But, after few days, there was flakiness observed in the tests and turned out that we need to do some dirstate dance as repo.dirstate.setparents() does not always fix the dirstate. That flakiness was a blocker for progress at that time and we decided to switch to amend back so that we can have things working with some hacks and we can later fix the implementation part. Now, yesterday while tackling resolving content-divergence of a stack which is as follows: C1 C2 | | B1 B2 | | A1 A2 \/ base where, A1-A2, B1-B2, C1-C2 are content-divergent with each other. Now we can resolve A1-A2 very well because they have the same parent and let's say that resolution leads to A3. Now, we want to resolve B1-B2 and make the new resolution commit on top of A3 so that we can end up something like: C3 | B3 | A3 | base however, amending one of the divergent changesets, it's not possible to create a commit on a different parent like A3 here without some relocation. We should prevent relocation as that may leads to some conflicts and should change the parent before committing. So, looking ahead, we can't move with using amend as still using that we will need some relocation hacks making code ugly and prone to bad behaviors, bugs. Let's change back to creating a new commit so that we can move forward in a good way. About repo.dirstate.setparents() not setting the dirstate, I have researched yesterday night about how we can do that and found out that we can use cmdrewrite._uncommitdirstate() here. Expect upcoming patches to improve the documentation of that function. There are lot of test changes because of change in hash but there is no behavior change. The only behavior change is in test-evolve-abort-contentdiv.t which is nice because creating a new commit helps us in stripping that while aborting. We have a lot of testing of content-divergence and no behavior change gives enough confidence for making this change. I reviewed the patch carefully to make sure there is no behavior change and I suggest reviewer to do the same.

This test file test the #5720 issue

Check that `hg evolve --continue` doesn't change changeset phase from secret
to draft after a merge conflict.

https://bz.mercurial-scm.org/show_bug.cgi?id=5720

Global setup
============

  $ . $TESTDIR/testlib/common.sh
  $ cat >> $HGRCPATH <<EOF
  > [ui]
  > interactive = true
  > [phases]
  > publish=False
  > [extensions]
  > evolve =
  > EOF

Test
====

  $ hg init $TESTTMP/issue-5720
  $ cd $TESTTMP/issue-5720

Create two drafts commits and one secret
  $ echo a > a
  $ hg commit -Am a
  adding a
  $ echo b > a
  $ hg commit -m b
  $ echo c > a
  $ hg commit --secret -m c
  $ hg log -G -T "{rev}: {phase}"
  @  2: secret
  |
  o  1: draft
  |
  o  0: draft
  
Amend the second draft with new content
  $ hg prev
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  [1] b
  $ echo b2 > a
  $ hg amend
  1 new orphan changesets
  $ hg log -G -T "{rev}: {phase}"
  @  3: draft
  |
  | *  2: secret
  | |
  | x  1: draft
  |/
  o  0: draft
  
Evolve which triggers a conflict
  $ hg evolve
  move:[2] c
  atop:[3] b
  merging a
  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
  abort: fix conflicts and see `hg help evolve.interrupted`
  [255]

Fix the conflict
  $ echo c2 > a
  $ hg resolve -m
  (no more unresolved files)
  continue: hg evolve --continue

Continue the evolution
  $ hg evolve --continue
  evolving 2:13833940840c "c"
  working directory is now at 3d2080c198e5

Tip should stay in secret phase
  $ hg log -G -T "{rev}: {phase}"
  @  4: secret
  |
  o  3: draft
  |
  o  0: draft
  
  $ hg log -r . -T '{phase}\n'
  secret