GHTable.rb

#!/usr/bin/env ruby
# encoding: utf-8

input = "a, b, c\nd, e, f\ng, h, i\n"
lines = input.split("\n")
rows = lines.map { |l| l.gsub(/ *, */, ' | ') }
col_count = rows.first.scan(/\|/).count + 1
with_header = rows.insert(1, "|#{'---|' * col_count}")
output = with_header.join("\n")
puts "output:\n#{output}"