Returns the current node or tag for the given path.

def find_hg_tag(path):
    """Returns the current node or tag for the given path."""
    tags = {}
    try:
        client = subprocess.Popen(
            ["hg", "cat", "-r", "tip", ".hgtags"], stdout=subprocess.PIPE, cwd=path
        )
        for line in client.communicate()[0].splitlines():
            line = line.strip()
            if not line:
                continue
            hash, tag = line.split()
            tags[hash] = tag
    except OSError:
        return

    client = subprocess.Popen(
        ["hg", "parent", "--template", "#node#"], stdout=subprocess.PIPE, cwd=path
    )

    tip = client.communicate()[0].strip()
    tag = tags.get(tip)
    if tag is not None:
        return tag
    return tip