Don't crash on last_node

lib/tree_builder.py

@@ -181,11 +181,12 @@ class TreeBuilder:
             node = merge_before_last.merged
             last_node = None
             while node:
+                last_node = node
                 node = node.parent
                 if node and node.merged_into:
                     break
-                last_node = node
-            last_node.parent = None
+            if last_node:
+                last_node.parent = None
 
         if not last_merge.parent:
             last_merge.parent = last_merge.merged
@@ -196,6 +197,7 @@ class TreeBuilder:
         """Create a Factory tree (returning the top)"""
         factory_revisions = self.revisions_chain("openSUSE:Factory", package)
         self.add_merge_points(factory_revisions)
-        #factory_revisions.print()
+        # factory_revisions.print()
         self.prune_loose_end(factory_revisions)
+        # factory_revisions.print()
         return factory_revisions

tests/fixtures/CoreFreq-expected-tree.yaml

@@ -0,0 +1,52 @@
+- commit: openSUSE:Factory/CoreFreq/15.0
+  merged:
+  - hardware/CoreFreq/32.0
+  - hardware/CoreFreq/31.0
+- commit: openSUSE:Factory/CoreFreq/14.0
+  merged:
+  - hardware/CoreFreq/29.0
+- commit: openSUSE:Factory/CoreFreq/13.0
+  merged:
+  - hardware/CoreFreq/27.0
+  - hardware/CoreFreq/26.0
+- commit: openSUSE:Factory/CoreFreq/12.0
+  merged:
+  - hardware/CoreFreq/25.0
+  - hardware/CoreFreq/24.0
+- commit: openSUSE:Factory/CoreFreq/11.0
+  merged:
+  - hardware/CoreFreq/23.0
+- commit: openSUSE:Factory/CoreFreq/10.0
+  merged:
+  - hardware/CoreFreq/22.0
+- commit: openSUSE:Factory/CoreFreq/9.0
+  merged:
+  - hardware/CoreFreq/21.0
+- commit: openSUSE:Factory/CoreFreq/8.0
+  merged:
+  - hardware/CoreFreq/20.0
+- commit: openSUSE:Factory/CoreFreq/7.0
+  merged:
+  - hardware/CoreFreq/18.0
+- commit: openSUSE:Factory/CoreFreq/6.0
+  merged:
+  - hardware/CoreFreq/16.0
+  - hardware/CoreFreq/15.0
+- commit: openSUSE:Factory/CoreFreq/5.0
+  merged:
+  - hardware/CoreFreq/13.0
+- commit: openSUSE:Factory/CoreFreq/4.0
+  merged:
+  - hardware/CoreFreq/11.0
+- commit: openSUSE:Factory/CoreFreq/3.0
+  merged:
+  - hardware/CoreFreq/9.0
+  - hardware/CoreFreq/8.0
+  - hardware/CoreFreq/7.0
+  - hardware/CoreFreq/6.0
+- commit: openSUSE:Factory/CoreFreq/2.0
+  merged:
+  - hardware/CoreFreq/4.0
+- commit: openSUSE:Factory/CoreFreq/1.0
+- commit: hardware/CoreFreq/2.0
+- commit: hardware/CoreFreq/1.0

tests/tree_test.py

@@ -45,5 +45,9 @@ class TestTreeMethods(unittest.TestCase):
     def test_2048_cli_tree(self):
         self.verify_package("2048-cli")
 
+    def test_corefreq_tree(self):
+        self.verify_package("CoreFreq")
+
+
 if __name__ == "__main__":
     unittest.main()