dirstate: fix filefoldmap incosistency on file delete The _filefoldmap is not updated in when files are deleted from dirstate. In the case where the file with the same but differently cased name is added afterwards it renders _filefoldmap incorrect. Those steps must occur to for a problem to reproduce: - call status (with listunknown=True), - update working rectory to a commit which does a casefolding change (A -> a) - call status again (it will show the file "a" as deleted) Unfortunately I'm unable to write a test for it because I don't know any core-mercurial command able to reproduce those steps. The bug was originally spotted when hgwatchman was enabled. It caused the changeset contents change during hg rebase (one file unrelarted to changeset was deleted in it after rebase). The hgwatchman is able to hit it because when hgignore changes the hgwatchmans overridestatus is calling original status with listunknown=True.