hexdump elides a partial last line with asterisk

[Ralph Corderoy]

Package bsdmainutils 8.2.3's hexdump(1) says

    -v Cause hexdump to display all input data. Without the -v
    option, any number of groups of output lines, which would be
    identical to the immediately preceding group of output lines (except
    for the input offsets), are replaced with a line comprised of a
    single asterisk.

(Aside: "immediately preceding group of output lines" is misleading, the
"*" always indicates just the last printed line is repeated, not a group
of them.)

This suggests it's as coreutils's od's -v/--output-duplicates but it
behaves differently.

    $ printf 0123456789abcdef0 | hd
    00000000 30 31 32 33 34 35 36 37 38 39 61 62 63 64 65 66 |0123456789abcdef|
    *
    00000011
    $

I have to subtract the address before the * from the one after to find
out the number of bytes that are the same as the previous fully-printed
line; in this case 1, the 0x30 byte.

Note, on some Ubuntus, e.g. 10.10, bsdmainutils 8.0.11ubuntu1, it's
worse as the final offset is incorrect.

    $ printf 0123456789abcdef0 | hd
    00000000 30 31 32 33 34 35 36 37 38 39 61 62 63 64 65 66 |0123456789abcdef|
    *
    00000010
    $

I've no way of knowing how many bytes have been elided.

Here's coreutils's od.

    $ s=0123456789abcdef
    $ printf ${s}0 | od -tx1
    0000000 30 31 32 33 34 35 36 37 38 39 61 62 63 64 65 66
    0000020 30
    0000021
    $ printf $s$s${s}0 | od -tx1
    0000000 30 31 32 33 34 35 36 37 38 39 61 62 63 64 65 66
    *
    0000060 30
    0000061
    $

Clearly, hexdump should print the trailing line of bytes in full if it's
an incomplete line just as coreutils's od does; I shouldn't have to do
arithmetic. However, if the current behaviour is deemed to be correct
then hexdump(1) needs correcting.