Workaround for truncation when writing file timestamps in Python

copy_mtime

def copy_mtime(src, dest):
    # Don't use os.utime() or shutil.copystat() -- these both truncate the
    # time due to python's float not having as much resolution as the
    # filesystem -- see http://ciaranm.wordpress.com/2009/11/15/this-week-in-python-stupidity-os-stat-os-utime-and-sub-second-timestamps/
    #
    # If the truncation during reading (from os.stat()) was the same as the
    # truncation during writing, the problem would be transparent here (but
    # would still affect other non-truncating code), however python takes the
    # problem to a new level and truncates an extra decimal place during write.
    # Either way, it's best to avoid the write truncation altogether.
    subprocess.check_call(["touch", "-r", src, dest])