name-rev: drop name_rev()'s 'generation' and 'distance' parameters

name-rev: drop name_rev()'s 'generation' and 'distance' parameters

Following the previous patches in this series we can get the values of
name_rev()'s 'generation' and 'distance' parameters from the 'stuct
rev_name' associated with the commit as well.

Let's simplify the function's signature and remove these two
unnecessary parameters.

Note that at this point we could do the same with the 'tip_name',
'taggerdate' and 'from_tag' parameters as well, but those parameters
will be necessary later, after the recursion is eliminated.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>