store: don't create dirs ending in period or space for hashed paths (
issue1417)
Windows won't create directories with names ending in period or space, so
we replace the last period/space character in truncated directory names of
hashed paths with some other character (underbar).
a -> a not a symlink
a -> b
Now at: base.patch
applying symlink.patch
Now at: symlink.patch
a -> b