hg evolve --continue and obsmarkers after conflict resolution with no changes to commit (issue5967)

https://bz.mercurial-scm.org/show_bug.cgi?id=5967

  $ . $TESTDIR/testlib/common.sh

  $ hg init issue5967

  $ cd issue5967

  $ cat > .hg/hgrc << EOF

  > [alias]

  > glog = log -GT "{rev}: {desc}"

  > [extensions]

  > evolve=

  > EOF

  $ echo apple > a

  $ hg ci -qAm 'apple'

  $ echo banana > a

  $ hg ci -m 'banana'

Amending revision 0 in a way that causes conflicts

  $ hg prev

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  [0] apple

  $ echo apricot > a

  $ hg amend -m 'apricot'

  1 new orphan changesets

  $ hg glog

  @  2: apricot

  *  1: banana

  |

  x  0: apple

Trying to evolve, then manually discarding changes from revision 1

  $ hg evolve

  move:[1] banana

  atop:[2] apricot

  merging a

  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')

  fix conflicts and see `hg help evolve.interrupted`

  [1]

  $ echo apricot > a

  $ hg resolve --mark a

  (no more unresolved files)

  continue: hg evolve --continue

This will correctly notice that revision 1 can be dropped

  $ hg evolve --continue

  evolving 1:dd9b5dd30cd6 "banana"

  evolution of 1:dd9b5dd30cd6 created no changes to commit

  working directory is now at 4d6fec23dcc4

  $ hg glog

  @  2: apricot

  $ hg olog --all

  |

  $ hg olog --hidden --all 1

  x  dd9b5dd30cd6 (1) banana