--- a/hgsubversion/pushmod.py
+++ b/hgsubversion/pushmod.py
@@ -97,8 +97,8 @@ def commit(ui, repo, rev_ctx, meta, base
     elif parent_branch and parent_branch != 'default':
         branch_path = 'branches/%s' % parent_branch
 
-    extchanges = list(svnexternals.diff(svnexternals.parse(parent),
-                                        svnexternals.parse(rev_ctx)))
+    extchanges = svnexternals.diff(svnexternals.parse(parent),
+                                   svnexternals.parse(rev_ctx))
     addeddirs, deleteddirs = _getdirchanges(svn, branch_path, parent, rev_ctx,
                                             rev_ctx.files(), extchanges)
     deleteddirs = set(deleteddirs)

--- a/hgsubversion/svnexternals.py
+++ b/hgsubversion/svnexternals.py
@@ -61,18 +61,20 @@ class externalsfile(dict):
                 self.setdefault(target, []).append(line[1:])
 
 def diff(ext1, ext2):
-    """Compare 2 externalsfile and yield tuples like (dir, value1, value2)
-    where value1 is the external value in ext1 for dir or None, and
-    value2 the same in ext2.
+    """Compare 2 externalsfile and return a list of tuples like (dir,
+    value1, value2) where value1 is the external value in ext1 for dir
+    or None, and value2 the same in ext2.
     """
+    changes = []
     for d in ext1:
         if d not in ext2:
-            yield d, '\n'.join(ext1[d]), None
+            changes.append((d, '\n'.join(ext1[d]), None))
         elif ext1[d] != ext2[d]:
-            yield d, '\n'.join(ext1[d]), '\n'.join(ext2[d])
+            changes.append((d, '\n'.join(ext1[d]), '\n'.join(ext2[d])))
     for d in ext2:
         if d not in ext1:
-            yield d, None, '\n'.join(ext2[d])
+            changes.append((d, None, '\n'.join(ext2[d])))
+    return changes
 
 class BadDefinition(Exception):
     pass