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
%% no changes
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%% uncompressed contents in repo
this is a test
%% uncompress our working dir copy
this is a test
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
%% uncompress our new working dir copy
this is a test