Generate copyright header author lists

authors.rb

#!/usr/bin/env ruby

# This script can be used to generate a list of authors for each source file,
# for inclusion in the copyright header.

require 'rugged'
require 'set'

repo = Rugged::Repository.new(".")

tree = repo.lookup(repo.head.target).tree
tree.each_blob { |entry|
    filename = entry[:name]

    if not filename.end_with? ".h", ".cpp" then
        next
    end

    authors = Hash.new # author name => set of years

    walker = Rugged::Walker.new(repo)
    walker.sorting(Rugged::SORT_TOPO | Rugged::SORT_REVERSE)
    walker.push(repo.head.target)

    walker.each { |commit|
        parents = commit.parents.map { |parent| parent.oid }
        if parents.length > 0 then
            sha1 = commit.oid
            sha2 = parents[0]
            if `git diff --name-only #{sha1} #{sha2}`.include? filename then
                author = "#{commit.author[:name]} <#{commit.author[:email]}>"
                year = commit.author[:time].to_s[0..3].to_i

                if authors.include? author then
                    authors[author] << year
                else
                    authors[author] = [year].to_set
                end
            end
        end
    }

    puts "\n * #{filename}"
    authors.each { |author, years|
        puts " * Copyright (c) #{years.to_a.sort.join(', ')} #{author}"
    }
}