sparse: fix debugrebuilddirsate when narrow extension is enabled
dirstate wrapping in narrow extension converts the manifest object to a list. So
let's assume we get a list of files in sparse extension.
Differential Revision: https://phab.mercurial-scm.org/D5481
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..