--- a/hgext3rd/evolve/evolvecmd.py	Wed Apr 29 00:44:14 2020 +0800
+++ b/hgext3rd/evolve/evolvecmd.py	Sat Mar 21 20:36:41 2020 +0100
@@ -122,28 +122,37 @@
     if not pctx.obsolete():
         ui.warn(_(b"cannot solve instability of %s, skipping\n") % orig)
         return (False, b".")
-    obs = pctx
-    try:
-        newer = utility._singlesuccessor(repo, obs)
-        # search of a parent which isn't the orig
-        while repo[newer].node() == orig.node():
-            obs = obs.parents()[0]
-            newer = utility._singlesuccessor(repo, obs)
-    except utility.MultipleSuccessorsError as exc:
-        if exc.divergenceflag:
+    targetancs = []
+    # Find successors of the changesets that cause the orphan. These will be
+    # the ancestors of the target (unless they are split over multiple
+    # topological branches, in which case we ask the user to choose one).
+    for obsrev in repo.revs(b'::%d and obsolete()', pctx.rev()):
+        obs = repo[obsrev]
+        succs = obsutil.successorssets(repo, obs.node())
+        if not succs:
+            continue
+        if len(succs) > 1:
             msg = _(b"skipping %s: divergent rewriting. can't choose "
                     b"destination\n") % obs
             ui.write_err(msg)
             return (False, b".")
-        if exc.splitflag:
-            splitsucc = utility.picksplitsuccessor(ui, repo, obs, orig)
-            if not splitsucc[0]:
+        targetancs.extend(node for node in succs[0] if node != orig.node())
+    if not targetancs:
+        # If no successors of the changesets that cause the orphan could be
+        # found, fall back to next non-obsolete ancestor.
+        newer = repo.revs(b'::%d and not obsolete()', pctx.rev()).last()
+        if newer is None:
+            newer = nodemod.nullid
+    else:
+        if True: # keep indentation for now
+            orphantarget = utility.pickorphantarget(ui, repo, targetancs, orig)
+            if not orphantarget[0]:
                 msg = _(b"could not solve instability, "
                         b"ambiguous destination: "
-                        b"parent split across two branches\n")
+                        b"ancestors split across different branches\n")
                 ui.write_err(msg)
                 return (False, b".")
-            newer = splitsucc[1]
+            newer = orphantarget[1]
     target = repo[newer]
     if not ui.quiet or confirm:
         repo.ui.write(_(b'move:'), label=b'evolve.operation')
@@ -1203,10 +1212,15 @@
         r = tovisit.pop()
         if r == -1:
             continue
+        ctx = repo[r]
+        if not (ctx.obsolete() or ctx.orphan()):
+            # None of the ancestors are obsolete, therefore we don't have to
+            # search them. The revision itself is a possible destination.
+            dest.add(r)
+            continue
+        tovisit.extend(parents(r))
         succsets = obsutil.successorssets(repo, tonode(r), cache=cache)
-        if not succsets:
-            tovisit.extend(parents(r))
-        else:
+        if succsets:
             # We should probably pick only one destination from split
             # (case where '1 < len(ss)'), This could be the currently tipmost
             # but logic is less clear when result of the split are now on
@@ -1214,7 +1228,7 @@
             for ss in succsets:
                 for n in ss:
                     dest.add(torev(n))
-    return dest
+    return set(repo.revs(b'heads(%ld::%ld)', dest, dest))
 
 def _handlenotrouble(ui, repo, allopt, revopt, anyopt, targetcat):
     """Used by the evolve function to display an error message when

--- a/hgext3rd/evolve/utility.py	Wed Apr 29 00:44:14 2020 +0800
+++ b/hgext3rd/evolve/utility.py	Sat Mar 21 20:36:41 2020 +0100
@@ -126,24 +126,21 @@
 
     return repo[newer[0][0]].rev()
 
-def picksplitsuccessor(ui, repo, ctx, evolvecand):
-    """choose a successor of ctx from split targets
+def pickorphantarget(ui, repo, targetancestors, evolvecand):
+    """choose a new target for an orphan changeset
 
-    Choose highest one if all successors are in a topological branch. And if
-    they are split over multiple topological branches, we ask user to choose
-    an evolve destination.
+    Choose highest one if all successors of its ancestors are in a topological
+    branch. And if they are on different topological branches, we ask the user
+    to choose an evolve destination.
 
-    Return (True, succ) unless split targets are split over multiple
-    topological branches and user didn't choose any evolve destination,
-    in which case return (False, '.')
+    Return (True, succ) unless successors of ancestors are on different
+    topological branches and user didn't choose any evolve destination, in
+    which case return (False, '.').
     """
-    targets = obsutil.successorssets(repo, ctx.node())[0]
-    assert targets
-    targetrevs = [repo[r].rev() for r in targets]
-    heads = repo.revs(b'heads(%ld::%ld)', targetrevs, targetrevs)
+    heads = repo.revs(b'heads(%ln::%ln)', targetancestors, targetancestors)
     if len(heads) > 1:
-        cheader = (_(b"ancestor of '%s' split over multiple topological"
-                     b" branches.\nchoose an evolve destination:") %
+        cheader = (_(b"successors of ancestors of %s are on different "
+                     b"topological branches\nchoose an evolve destination:") %
                    evolvecand)
         selectedrev = revselectionprompt(ui, repo, list(heads), cheader)
         if selectedrev is None:

--- a/tests/test-evolve-issue5832.t	Wed Apr 29 00:44:14 2020 +0800
+++ b/tests/test-evolve-issue5832.t	Sat Mar 21 20:36:41 2020 +0100
@@ -107,7 +107,7 @@
   move:[2] added b
   atop:[5] added a
   hg rebase -r a1da0651488c -d 7014ec2829cd
-  could not solve instability, ambiguous destination: parent split across two branches
+  could not solve instability, ambiguous destination: ancestors split across different branches
 
 Resolving instability using `hg evolve`
 
@@ -117,7 +117,7 @@
   move:[2] added b
   atop:[5] added a
   move:[4] merge commit
-  ancestor of '7235ef625ea3' split over multiple topological branches.
+  successors of ancestors of 7235ef625ea3 are on different topological branches
   choose an evolve destination:
   1: [62fb70414f99] added c
   2: [5841d7cf9893] added d
@@ -249,7 +249,7 @@
   move:[2] added b
   atop:[6] added a
   hg rebase -r a1da0651488c -d 5568b87b1491
-  could not solve instability, ambiguous destination: parent split across two branches
+  could not solve instability, ambiguous destination: ancestors split across different branches
 
   $ hg evolve --any --all --config ui.interactive=True <<EOF
   > 2
@@ -257,7 +257,7 @@
   move:[2] added b
   atop:[6] added a
   move:[4] merge commit
-  ancestor of 'cdf2ea1b9312' split over multiple topological branches.
+  successors of ancestors of cdf2ea1b9312 are on different topological branches
   choose an evolve destination:
   1: [62fb70414f99] added c
   2: [5841d7cf9893] added d
@@ -395,14 +395,14 @@
   move:[2] added b
   atop:[6] added a
   hg rebase -r a1da0651488c -d 5568b87b1491
-  could not solve instability, ambiguous destination: parent split across two branches
+  could not solve instability, ambiguous destination: ancestors split across different branches
 
   $ hg evolve --any --all --config ui.interactive=True <<EOF
   > 2
   > EOF
   move:[2] added b
   atop:[6] added a
-  ancestor of 'b9b387427a53' split over multiple topological branches.
+  successors of ancestors of b9b387427a53 are on different topological branches
   choose an evolve destination:
   1: [62fb70414f99] added c
   2: [5841d7cf9893] added d

--- a/tests/test-evolve-orphan-split.t	Wed Apr 29 00:44:14 2020 +0800
+++ b/tests/test-evolve-orphan-split.t	Sat Mar 21 20:36:41 2020 +0100
@@ -193,7 +193,7 @@
   $ hg evolve --dry-run <<EOF
   > 1
   > EOF
-  ancestor of 'd48a30875f01' split over multiple topological branches.
+  successors of ancestors of d48a30875f01 are on different topological branches
   choose an evolve destination:
   1: [f2632392aefe] added a b c
   2: [7f87764e5b64] added a b c
@@ -206,7 +206,7 @@
   $ hg evolve --dry-run <<EOF
   > 2
   > EOF
-  ancestor of 'd48a30875f01' split over multiple topological branches.
+  successors of ancestors of d48a30875f01 are on different topological branches
   choose an evolve destination:
   1: [f2632392aefe] added a b c
   2: [7f87764e5b64] added a b c
@@ -222,56 +222,56 @@
   $ hg evolve --all <<EOF
   > foo
   > EOF
-  ancestor of 'd48a30875f01' split over multiple topological branches.
+  successors of ancestors of d48a30875f01 are on different topological branches
   choose an evolve destination:
   1: [f2632392aefe] added a b c
   2: [7f87764e5b64] added a b c
   q: quit the prompt
   enter the index of the revision you want to select: foo
   invalid value 'foo' entered for index
-  could not solve instability, ambiguous destination: parent split across two branches
+  could not solve instability, ambiguous destination: ancestors split across different branches
 
   $ hg evolve --all <<EOF
   > 4
   > EOF
-  ancestor of 'd48a30875f01' split over multiple topological branches.
+  successors of ancestors of d48a30875f01 are on different topological branches
   choose an evolve destination:
   1: [f2632392aefe] added a b c
   2: [7f87764e5b64] added a b c
   q: quit the prompt
   enter the index of the revision you want to select: 4
   invalid value '4' entered for index
-  could not solve instability, ambiguous destination: parent split across two branches
+  could not solve instability, ambiguous destination: ancestors split across different branches
 
   $ hg evolve --all <<EOF
   > -1
   > EOF
-  ancestor of 'd48a30875f01' split over multiple topological branches.
+  successors of ancestors of d48a30875f01 are on different topological branches
   choose an evolve destination:
   1: [f2632392aefe] added a b c
   2: [7f87764e5b64] added a b c
   q: quit the prompt
   enter the index of the revision you want to select: -1
   invalid value '-1' entered for index
-  could not solve instability, ambiguous destination: parent split across two branches
+  could not solve instability, ambiguous destination: ancestors split across different branches
 
   $ hg evolve --all <<EOF
   > q
   > EOF
-  ancestor of 'd48a30875f01' split over multiple topological branches.
+  successors of ancestors of d48a30875f01 are on different topological branches
   choose an evolve destination:
   1: [f2632392aefe] added a b c
   2: [7f87764e5b64] added a b c
   q: quit the prompt
   enter the index of the revision you want to select: q
-  could not solve instability, ambiguous destination: parent split across two branches
+  could not solve instability, ambiguous destination: ancestors split across different branches
 
 Doing the evolve with the interactive prompt
 
   $ hg evolve --all <<EOF
   > 1
   > EOF
-  ancestor of 'd48a30875f01' split over multiple topological branches.
+  successors of ancestors of d48a30875f01 are on different topological branches
   choose an evolve destination:
   1: [f2632392aefe] added a b c
   2: [7f87764e5b64] added a b c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-evolve-orphan-switched-ancestors.t	Sat Mar 21 20:36:41 2020 +0100
@@ -0,0 +1,37 @@
+  $ . $TESTDIR/testlib/common.sh
+  $ cat >> $HGRCPATH <<EOF
+  > [extensions]
+  > evolve=
+  > [alias]
+  > glog = log -GT "{rev}:{node|short} {desc}\n"
+  > EOF
+
+Test that, even if the order of the ancestors has been switched, the orphan is
+rebased such that it has the sucessors of both original ancestors are the new
+ancestors.
+
+  $ hg init repo
+  $ cd repo
+  $ mkcommit a
+  $ mkcommit b
+  $ echo a1 > a; echo b1 > b; hg ci -m 'mod ab'
+  $ hg up null -q
+  $ hg pick 1
+  picking 1:d2ae7f538514 "b"
+  1 new orphan changesets
+  $ hg pick 0
+  picking 0:cb9a9f314b8b "a"
+  $ hg next --dry-run
+  move:[2] mod ab
+  atop:[4] a
+  hg rebase -r cc6607605d1e -d f4a8092719b1
+  $ hg evolve
+  move:[2] mod ab
+  atop:[4] a
+  $ hg glog
+  o  5:866738c73814 mod ab
+  |
+  @  4:f4a8092719b1 a
+  |
+  o  3:6563da9dcf87 b
+