Find the last page of commits to master for a given github repository

last_page.rb

#!/usr/bin/env ruby

user, repo = ARGV

if `which curl`.length == 0
    puts "please install curl"
    exit 1
end

repo_loc = "https://github.com/#{user}/#{repo}"
base_url = "#{repo_loc}/commits/master?page="

def is_404(url)
    `curl -s --head #{url} | head -n1` =~ /404 Not Found/
end

if is_404(repo_loc)
    puts "#{user} #{repo} could not be found on GitHub"
    exit 2
end

lo = 1
hi = 500

while lo <= hi do
    page_num = (lo+hi)/2
    if is_404 "#{base_url}#{page_num}"
        puts "didn't find #{page_num}"
        hi = page_num - 1
        minus = 1
    else
        puts "found #{page_num}"
        lo = page_num + 1
        minus = 0
    end
end

puts "#{base_url}#{page_num-minus}"