dirstate: eliminate reference cycle from normalize
Bound methods hold a reference to self, so assigning a bound method to
an instance unavoidably creates a cycle. Work around this by choosing
a normalize method at walk time instead. Eliminate default arg while
we're at it.
hg: config error at .../t/.hg/hgrc:1: 'invalid'
updating working directory
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
[paths]
default = .../foo%bar
default = .../foo%bar
bundle.mainreporoot=.../foobar
defaults.backout=-d "0 0"
defaults.commit=-d "0 0"
defaults.tag=-d "0 0"
paths.default=.../foo%bar
ui.slash=True