merge: remember rename copies and parents properly on commit record copies in dirstate even if rename was remote this lets us record it properly at commit teach checkfilemerge about copies, including merge cases pull old copy code out of commit extend rename-merge1 test to show file index

# 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