command line templates: add formatnode filter
This will print a full hash node with --debug and a short one otherwise.
Use it with some default templates and in map-cmdline.default to print
the parents. This should fix
issue538.
util.opener: if requested, use atomicfile even if the file doesn't exist
Right now, surprisingly enough, if you request an atomic file but the
file still doesn't exist, you get a regular file. AFAICS, the only time
this happens is during the initial creation of the dirstate.