Orphan changeset and trying to relocate a node on top of itself (issue6097)

https://bz.mercurial-scm.org/show_bug.cgi?id=6097

  $ . $TESTDIR/testlib/common.sh

  $ cat << EOF >> $HGRCPATH

  > [extensions]

  > rebase =

  > evolve =

  > EOF

  $ hg init issue6097

  $ cd issue6097

  $ echo apricot > a

  $ hg ci -qAm apricot

  $ echo banana > b

  $ hg ci -qAm banana

Let's go back to amend 0 and make an orphan out of 1

  $ hg up -q 0

  $ echo coconut > c

  $ hg add -q c

  $ hg ci --amend -m 'apricot and coconut'

  1 new orphan changesets

Now rebase the successor of 0 on top of 1

  $ hg rebase -r . -d 1

  rebasing 2:32acf8fb1b23 "apricot and coconut" (tip)

  1 new orphan changesets

Pruning 1 just to get it out of the way

  $ hg prune -q 1

Note how both the regular DAG and the obsolescence graph are linear, but the

paths from 3 to 0 are different: 3-1-0 and 3-2-0

  $ hg log -G

  @  changeset:   3:2868fe6df617

  |  tag:         tip

  |  parent:      1:e0486f65907d

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  instability: orphan

  |  summary:     apricot and coconut

  |

  x  changeset:   1:e0486f65907d

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  obsolete:    pruned using prune

  |  summary:     banana

  |

  x  changeset:   0:692cc7b6212c

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     obsolete:    rewritten using amend, rebase as 3:2868fe6df617

     summary:     apricot

  $ hg obslog

  @  2868fe6df617 (3) apricot and coconut

  |

  x  32acf8fb1b23 (2) apricot and coconut

  |    rewritten(parent, content) as 2868fe6df617 using rebase by test (Thu Jan 01 00:00:00 1970 +0000)

  |

  x  692cc7b6212c (0) apricot

       rewritten(description, content) as 32acf8fb1b23 using amend by test (Thu Jan 01 00:00:00 1970 +0000)

FIXME: obviously a traceback is not good

  $ hg evolve -r . 2>&1 | grep '^\S'

  move:[3] apricot and coconut

  atop:[3] apricot and coconut

  ** unknown exception encountered, please report by visiting

  ** https://mercurial-scm.org/wiki/BugTracker

  ** Python * (glob)

  ** Mercurial Distributed SCM (*) (glob)

  ** Extensions loaded: rebase, evolve

  ** ProgrammingError: tried to relocate a node on top of itself

  ** (This shouldn't happen. If you still need to move changesets, please do so manually with nothing to rebase - working directory parent is also destination)

  Traceback (most recent call last):

  mercurial.error.ProgrammingError: tried to relocate a node on top of itself