./thisscript.rb 10
will add up the patch stats for the last 10 commits
to the current darcs repo. this differs from the results
for a simple `diff -u --last` as this is the minimal patch
set whereas the script below stats the "edits patch"

#!/usr/bin/ruby
hashes=[]
changelist=`darcs changes --last #{ARGV.first} --xml`
changelist.each_line {
   |line|
   next unless line =~ /hash='(.*?).gz'/
   hashes << $1
}
added, removed = 0, 0
hashes.each {
   |hash|
   diff=`darcs annotate --match "hash #{hash}"`
   diff.each_line {
      |l|
      added   += 1 if l =~ /^[-]/
      removed += 1 if l =~ /^[+]/
   }
}
puts "+#{added} -#{removed}"