git-diff-blame.pl

#!/usr/bin/perl -w

# This is derived from the script posted by Thomas Rast in this mailing list post:
# http://n2.nabble.com/Blamming-a-diff-between-two-commits-td2340836.html

sub parse_hunk_header {
        my ($line) = @_;
        my ($o_ofs, $o_cnt, $n_ofs, $n_cnt) =
            $line =~ /^@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@/;
        $o_cnt = 1 unless defined $o_cnt;
        $n_cnt = 1 unless defined $n_cnt;
        return ($o_ofs, $o_cnt, $n_ofs, $n_cnt);
}

sub get_blame_prefix {
        my ($line) = @_;
        $line =~ /^(\^?[0-9a-f]+[^\(]+\([^\)]+\))/ or die "bad blame output: $line";
        return $1;
}

my ($newrev) = @ARGV;
my $oldrev = "$newrev^";
open($diff, '-|', 'git', '--no-pager', 'diff', '-U0', '--diff-filter=MD', $oldrev, $newrev) or die;

my ($pre, $post);
my $filename;

print "Commit $newrev\n";

while (<$diff>) {
        if (m{^diff --git ./(.*) ./\1$}) {
                $filename = $1;
        } elsif (m{^(\+\+\+|---) ./$filename$}) {
                # ignore
        } elsif (m{^@@ }) {
                my ($o_ofs, $o_cnt, $n_ofs, $n_cnt)
                        = parse_hunk_header($_);
                my $o_end = $o_ofs + $o_cnt;
                my $n_end = $n_ofs + $n_cnt;
                open($pre, '-|', 'git', 'blame', "-L$o_ofs,$o_end", $oldrev,'-w','-C','-M','-f', 
                     '--', $filename) or die "$oldrev..$newrev";
        } elsif (m{^ }) {
                print get_blame_prefix(scalar <$pre>), "\t", $_;
                scalar <$post>; # discard
        } elsif (m{^\-}) {
                print get_blame_prefix(scalar <$pre>), "\t", $_;
        }
} 

print "\n";