Fix cold cache diff performance cold cache diff performance has regressed in two ways. localrepo.changes has optimizations for diffing against the working dir parent that expect node1 to be None. commands.revpair() usage means that commands.dodiff() never sends node1 == None. This is fixed in localrepo.changes by checking against the dirstate parents. In the non-dirstate parents case, localrepo.changes does a loop comparing files without first sorting the file names, leading to random access across the disk.

# should print nothing
# should print ? b/x
? b/x
# should print A b/x
A b/x
# should forget b/x
forgetting b/x
# should print nothing