--- a/hgext3rd/topic/stack.py	Mon Aug 15 01:50:15 2016 +0200
+++ b/hgext3rd/topic/stack.py	Mon Aug 15 05:15:19 2016 +0200
@@ -2,13 +2,12 @@
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
-import collections
 from mercurial.i18n import _
 from mercurial import (
     error,
     node,
-    obsolete,
 )
+from .evolvebits import builddependencies, _orderrevs, _singlesuccessor
 
 def getstack(repo, topic):
     # XXX need sorting
@@ -80,96 +79,3 @@
 
     return data
 
-# Copied from evolve 081605c2e9b6
-
-def _orderrevs(repo, revs):
-    """Compute an ordering to solve instability for the given revs
-
-    revs is a list of unstable revisions.
-
-    Returns the same revisions ordered to solve their instability from the
-    bottom to the top of the stack that the stabilization process will produce
-    eventually.
-
-    This ensures the minimal number of stabilizations, as we can stabilize each
-    revision on its final stabilized destination.
-    """
-    # Step 1: Build the dependency graph
-    dependencies, rdependencies = builddependencies(repo, revs)
-    # Step 2: Build the ordering
-    # Remove the revisions with no dependency(A) and add them to the ordering.
-    # Removing these revisions leads to new revisions with no dependency (the
-    # one depending on A) that we can remove from the dependency graph and add
-    # to the ordering. We progress in a similar fashion until the ordering is
-    # built
-    solvablerevs = [r for r in sorted(dependencies.keys())
-                    if not dependencies[r]]
-    ordering = []
-    while solvablerevs:
-        rev = solvablerevs.pop()
-        for dependent in rdependencies[rev]:
-            dependencies[dependent].remove(rev)
-            if not dependencies[dependent]:
-                solvablerevs.append(dependent)
-        del dependencies[rev]
-        ordering.append(rev)
-
-    ordering.extend(sorted(dependencies))
-    return ordering
-
-def builddependencies(repo, revs):
-    """returns dependency graphs giving an order to solve instability of revs
-    (see _orderrevs for more information on usage)"""
-
-    # For each troubled revision we keep track of what instability if any should
-    # be resolved in order to resolve it. Example:
-    # dependencies = {3: [6], 6:[]}
-    # Means that: 6 has no dependency, 3 depends on 6 to be solved
-    dependencies = {}
-    # rdependencies is the inverted dict of dependencies
-    rdependencies = collections.defaultdict(set)
-
-    for r in revs:
-        dependencies[r] = set()
-        for p in repo[r].parents():
-            try:
-                succ = _singlesuccessor(repo, p)
-            except MultipleSuccessorsError as exc:
-                dependencies[r] = exc.successorssets
-                continue
-            if succ in revs:
-                dependencies[r].add(succ)
-                rdependencies[succ].add(r)
-    return dependencies, rdependencies
-
-def _singlesuccessor(repo, p):
-    """returns p (as rev) if not obsolete or its unique latest successors
-
-    fail if there are no such successor"""
-
-    if not p.obsolete():
-        return p.rev()
-    obs = repo[p]
-    ui = repo.ui
-    newer = obsolete.successorssets(repo, obs.node())
-    # search of a parent which is not killed
-    while not newer:
-        ui.debug("stabilize target %s is plain dead,"
-                 " trying to stabilize on its parent\n" %
-                 obs)
-        obs = obs.parents()[0]
-        newer = obsolete.successorssets(repo, obs.node())
-    if len(newer) > 1 or len(newer[0]) > 1:
-        raise MultipleSuccessorsError(newer)
-
-    return repo[newer[0][0]].rev()
-
-class MultipleSuccessorsError(RuntimeError):
-    """Exception raised by _singlesuccessor when multiple successor sets exists
-
-    The object contains the list of successorssets in its 'successorssets'
-    attribute to call to easily recover.
-    """
-
-    def __init__(self, successorssets):
-        self.successorssets = successorssets