#! /usr/bin/perl

my (%Y, %M);
open my $fh, "-|", "git", "log",
  "--date=format:%Y", "--pretty=format:%ad %aN", @ARGV
  or die "git log: $!";
while (<$fh>) {
  /(\d+)\s+(.*)$/ or die "wtf?  $_";
  my ($y, $who) = ($1, $2);
  push @{$Y{$who}}, $y;
  if (!exists $M{$who} || $y < $M{$who}) { $M{$who} = $y; }
}
close $fh or die "git log (rc = $?)";

my ($S, $O, $L);
sub out () {
  defined $L or return;
  defined $S and $S .= ", ";
  if ($O < $L - 1) { $S .= "$O--$L" }
  elsif ($O != $L) { $S .= "$O, $L" }
  else { $S .= "$L" }
}

for my $who (sort { $M{$a} <=> $M{$b} } keys %Y) {
  my @y = sort { $a <=> $b } @{$Y{$who}};
  undef $S; undef $L;
  for my $y (@y) {
    if (!defined $L) { $O = $L = $y; }
    elsif ($y == $L + 1) { $L = $y; }
    elsif ($y != $L) { out(); $O = $L = $y; }
  }
  out();
  print "$who: $S\n"
}