You can have something like that also in your shell. Just apply

  git log --reverse | perl githead.pl

where githead.pl is

  my $date, $old; while (my $line = <>) { chomp $line; next unless $line; $date = "$1 $2 $3" if $line =~ m|Date:\s+(.+?)\s+(.+?)\s+(.+?)\s+|; if ($line =~ m/^\s+/) { if ($date ne $old) { printf("%-10s%s\n",$date,$line); $old = $date; } else { printf("%-10s%s\n",'',$line); }}}