Code review comment for lp:~parthm/bzr/no-chown-if-bzrlog-exists

This can be done completely non-racily with os.open - a really picky version could be a function something like:

    lomode = os.O_WRONLY | os.O_APPEND | osutils.O_TEXT
    while True:
        try:
            return os.open(filename, lomode)
        except OSError, e:
            if e.errno != errno.ENOENT:
                raise
        try:
            fd = os.open(filename, lomode | os.O_CREAT | os.O_EXCL)
        except OSError, e:
            if e.errno != errno.EEXIST:
                raise
        else:
            copy_ownership(filename, ownership_src)
            return fd

And os.fdopen to make a regular file object.

Raises the question though, is it ever going to be right for a osutils.open_with_ownership function to chown the file if it's *not* just created it? Makes me wonder again whether bundling the chown into the open function makes any sense.