Fix find_in_path not including some file extension logic under win32.
Windows shell resolves utility path by combining PATH, the utility name and a set of file extensions from PATHEXT.
#!/bin/sh
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i