tests: test divergence created during interrupted rebase

If a rebase runs into conflicts and the user somehow rewrites an
unrebased commit in the rebase set while the rebase is interrupted,
continuing it might result in divergence. It turns out that we decide
to skip the commit. That seems to make sense, but it wasn't obvious to
me that that's what we should do. Either way, this patch adds a test
case for the current behavior.

Differential Revision: https://phab.mercurial-scm.org/D10256

tests/test-rebase-obsolete3.t

@@ -282,6 +282,49 b' issue5782'
   
   $ cd ..
 
+Start a normal rebase. When it runs into conflicts, rewrite one of the
+commits in the rebase set, causing divergence when the rebase continues.
+
+  $ hg init $TESTTMP/new-divergence-after-conflict
+  $ cd $TESTTMP/new-divergence-after-conflict
+  $ hg debugdrawdag <<'EOS'
+  >  C2
+  >  | C1
+  >  |/
+  >  B # B/D=B
+  >  | D
+  >  |/
+  >  A
+  > EOS
+  $ hg rebase -r B::C1 -d D
+  rebasing 1:2ec65233581b B "B"
+  merging D
+  warning: conflicts while merging D! (edit, then use 'hg resolve --mark')
+  unresolved conflicts (see 'hg resolve', then 'hg rebase --continue')
+  [240]
+  $ hg debugobsolete $(hg log -r C1 -T '{node}') $(hg log -r C2 -T '{node}')
+  1 new obsolescence markers
+  obsoleted 1 changesets
+  $ hg log -G
+  o  4:fdb9df6b130c C2
+  |
+  | x  3:7e5bfd3c08f0 C1 (rewritten as 4:fdb9df6b130c)
+  |/
+  | @  2:b18e25de2cf5 D
+  | |
+  % |  1:2ec65233581b B
+  |/
+  o  0:426bada5c675 A
+  
+  $ echo resolved > D
+  $ hg resolve -m D
+  (no more unresolved files)
+  continue: hg rebase --continue
+  $ hg rebase -c
+  rebasing 1:2ec65233581b B "B"
+  note: not rebasing 3:7e5bfd3c08f0 C1 "C1" and its descendants as this would cause divergence
+  1 new orphan changesets
+
 Rebase merge where successor of one parent is equal to destination (issue5198)
 
   $ hg init p1-succ-is-dest