[StGit PATCH 11/13] Check bottom and invariants

["David Kågedal" <davidk@lysator.liu.se>]

This code adds some checks that the bottom is actually always the
parent of top.

It also checks that the top is the same as what the patch ref points
to.

This is only do to ensure that the next patches are correct.

Signed-off-by: David Kågedal <davidk@lysator.liu.se>
---

 stgit/stack.py |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)


diff --git a/stgit/stack.py b/stgit/stack.py
index fdff5a4..d9a2e56 100644
--- a/stgit/stack.py
+++ b/stgit/stack.py
@@ -197,9 +197,15 @@ class Patch(StgitObject):
             self.__update_top_ref(top)
 
     def get_old_bottom(self):
-        return self._get_field('bottom.old')
+        old_bottom = self._get_field('bottom.old')
+        old_top = self.get_old_top()
+        assert old_bottom == git.get_commit(old_top).get_parent()
+        return old_bottom
 
     def get_bottom(self):
+        bottom = self._get_field('bottom')
+        top = self.get_top()
+        assert bottom == git.get_commit(top).get_parent()
         return self._get_field('bottom')
 
     def set_bottom(self, value, backup = False):
@@ -212,7 +218,13 @@ class Patch(StgitObject):
         return self._get_field('top.old')
 
     def get_top(self):
-        return self._get_field('top')
+        top = self._get_field('top')
+        try:
+            ref = git.rev_parse(self.__top_ref)
+        except:
+            ref = None
+        assert not ref or top == ref
+        return top
 
     def set_top(self, value, backup = False):
         if backup:
@@ -220,6 +232,7 @@ class Patch(StgitObject):
             self._set_field('top.old', curr)
         self._set_field('top', value)
         self.__update_top_ref(value)
+        self.get_bottom() # check the assert
 
     def restore_old_boundaries(self):
         bottom = self._get_field('bottom.old')