_slot_confict_backtrack: simplify code

The order of backtrack_data is simply based on version comparison
since commit 9b6f69e2a66c0f1d1d6545208edb3c45eacfd845.

diff --git a/pym/_emerge/depgraph.py b/pym/_emerge/depgraph.py
index 39ae3eab8bdfcffc49d0fd292531dbe27dc11266..4f9d0f02765effe81169134c0f305bb9efab4c7c 100644 (file)
--- a/pym/_emerge/depgraph.py
+++ b/pym/_emerge/depgraph.py
@@ -6,7 +6,6 @@ from __future__ import print_function, unicode_literals
 import errno
 import io
 import logging
-import operator
 import stat
 import sys
 import textwrap
@@ -959,20 +958,11 @@ class depgraph(object):
 
                debug = "--debug" in self._frozen_config.myopts
                existing_node = self._dynamic_config._slot_pkg_map[root][slot_atom]
+               # In order to avoid a missed update, first mask lower versions
+               # that conflict with higher versions (the backtracker visits
+               # these in reverse order).
+               conflict_pkgs.sort(reverse=True)
                backtrack_data = []
-               # The ordering of backtrack_data can make
-               # a difference here, because both mask actions may lead
-               # to valid, but different, solutions and the one with
-               # 'existing_node' masked is usually the better one. Because
-               # of that, we choose an order such that
-               # the backtracker will first explore the choice with
-               # existing_node masked. The backtracker reverses the
-               # order, so the order it uses is the reverse of the
-               # order shown here. See bug #339606.
-               if existing_node in conflict_pkgs and \
-                       existing_node is not conflict_pkgs[-1]:
-                       conflict_pkgs.remove(existing_node)
-                       conflict_pkgs.append(existing_node)
                for to_be_masked in conflict_pkgs:
                        # For missed update messages, find out which
                        # atoms matched to_be_selected that did not
@@ -983,11 +973,6 @@ class depgraph(object):
                                if parent_atom not in parent_atoms)
                        backtrack_data.append((to_be_masked, conflict_atoms))
 
-               if len(backtrack_data) > 1:
-                       # In order to avoid a missed update, first mask lower
-                       # versions that conflict with higher versions.
-                       backtrack_data.sort(key=operator.itemgetter(0), reverse=True)
-
                to_be_masked = backtrack_data[-1][0]
 
                self._dynamic_config._backtrack_infos.setdefault(