coreutils-4.5.7: df broken on unmounted devices

[Bruno Haible]

Hi,

This change:
  * df now displays a mount point (usually `/') for non-mounted
    character-special and block files
is counter-intuitive, because it produces

$ df /dev/hda
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda               2208864   2127604     81260  97% /
$ df /
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda3              2208864   2127604     81260  97% /

leaving the user puzzled about which device / corresponds to. It also
violates the spirit of POSIX:2001, which says:

    "%s %d %d %d %d%% %s\n", <file system name>, <total space>,
    <space used>, <space free>, <percentage used>,
    <file system root>

    ...

    <file system name> The name of the file system, in an implementation-
    defined format.

    <file system root> The directory below which the file system hierarchy
    appears.

So it is clearly understood that the first column should be the "name"
of the filesystem whose mount point is listed in the last column.
That's also what the header of the last column ("Mounted on") says, after all.

We already have

$ df /etc/profile
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda3              2208864   2127604     81260  97% /

Therefore a user (and also shell scripts which use the "df" output) will
expect

$ df /dev/tty
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda3              2208864   2127604     81260  97% /

instead of

$ df /dev/tty
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/tty               2208864   2127604     81260  97% /

Bruno