svn revision checkout -- checkout specific revision and (most importantly) checkout matching externals revision; useful if your repository has HEAD-tracking externals, but you want to compile an earlier version

svn-rco.rb

#!/usr/bin/env ruby

require 'uri'

def params_valid?
  lengthOkay = [2,3].include? ARGV.length
     revOkay = ARGV[0].to_i.to_s == ARGV[0]
     
  lengthOkay && revOkay
end

def date_for_svn_revision(url, revision)
  output = `svn log --limit 1 -r #{revision} '#{url}' --xml | grep '<date>.*</date>'`
  date = output.strip[/^<date>(.*)<\/date>$/, 1].strip rescue nil
end

def parse_externals(line)
  # http://svnbook.red-bean.com/en/1.7/svn.advanced.externals.html
  
  # good enough(tm) for my purposes
  name, url = line.split("\s")
end

def get_svn(url, path, date)
  output = `svn checkout --ignore-externals --revision '{#{date}}' "#{url}" "#{path}"`
  puts "  -- START --"
  puts "URL: #{url}", "path: #{path}", "date: #{date}"
  puts output
  puts "  -- END --"
  
  Dir.chdir(path) do
    output = `svn propget 'svn:externals'`.strip
    
    return if output.length == 0
    
    externals = output.lines.collect { |line| parse_externals(line) }.compact
    
    externals.each do |name, url|
      get_svn(url, name, date)
    end
  end
end

unless params_valid?
  puts "Usage: #{File.basename __FILE__} #revision URL [path]"
  exit 1
end

revision = ARGV[0].to_i
url      = URI.parse(ARGV[1])
path     = ARGV[2] || File.basename(url.path) || "checkout_#{url.host}_#{revision}"

date     = date_for_svn_revision(url, revision)

if date.nil? or date.length == 0
  puts "ERROR: could not find date for r#{revision} @ #{url}"
  puts "\tmost likely the corresponding commit did not touch the provided path"
  exit 2
end

get_svn url, path, date

you.. poor.. gitless.. aaaww