[MERGE] Handle empty list like non-empty list in iter_changes, revert

[Ian Clatworthy]

Ian Clatworthy has voted approve.
Status is now: Approved
Comment:
Looks good. My only comment is that test_no_specific_files in 
test_compare.py is almost identical to the routine just above it - 
test_empty_to_abc_content. Given that, I think the two tests should be 
testing for expected_results in the same way. It's very minor but right 
now, one sorts then compares and one doesn't. Please tweak if you think 
it's worth it.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C46D5DC80.9090708%40utoronto.ca%3E