Fix undo after aborted commit bug
Commit would overwrite undo.dirstate unconditionally, so an undo after
an aborted commit would restore the dirstate from the aborted commit
and not the prior transaction.
This copies dirstate to journal.dirstate and moves it after a
successful transaction.
+ hg init
+ echo This is file a1
+ hg add a
+ hg commit -m 'commit #0' -d '0 0'
+ echo This is file b1
+ hg add b
+ hg commit -m 'commit #1' -d '0 0'
+ hg update 0
+ echo This is file c1
+ hg add c
+ hg commit -m 'commit #2' -d '0 0'
+ hg update -m 1
+ rm b
+ echo This is file c22
+ hg commit -m 'commit #3' -d '0 0'