[PATCH V2] dirstate: fix filefoldmap incosistency on file delete

[Yuya Nishihara]

On Fri, 6 Nov 2015 12:32:03 -0800, Mateusz Kwapich wrote:
> # HG changeset patch
> # User Mateusz Kwapich <mitrandir at fb.com>
> # Date 1446841908 28800
> #      Fri Nov 06 12:31:48 2015 -0800
> # Node ID 91a3d774f808a3aa14c0786018da0abc1c5e8055
> # Parent  f9984f76fd90e439221425d751e29bae17bec995
> 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.
> 
> diff --git a/mercurial/dirstate.py b/mercurial/dirstate.py
> --- a/mercurial/dirstate.py
> +++ b/mercurial/dirstate.py
> @@ -536,6 +536,11 @@
>          if size == 0 and f in self._copymap:
>              del self._copymap[f]
>  
> +        if "_filefoldmap" in self.__dict__:
> +            normed = util.normcase(f)
> +            if normed in self._filefoldmap:
> +                del self._filefoldmap[normed]
> +
>      def merge(self, f):
>          '''Mark a file merged.'''
>          if self._pl[1] == nullid:
> @@ -549,6 +554,11 @@
>              self._droppath(f)
>              del self._map[f]
>  
> +        if "_filefoldmap" in self.__dict__:
> +            normed = util.normcase(f)
> +            if normed in self._filefoldmap:
> +                del self._filefoldmap[normed]

Looks good, but perhaps we can move them to _droppath(f) ?