creates/overwrites a file named <username>-<gemspec_file> and updates the s.name in there have the same project name format.

githubify.rb

#!/usr/bin/env ruby
# Usage: githubify <gemspec_file> [username]
# Requires: github.name to be set for the current git project or [username] to be specified
# Result: creates/overwrites a file named <username>-<gemspec_file> and updates the s.name in there have the same project name format.
#
# Author: Wes Oldenbeuving
# E-mail: narnach@gmail.com
# License: MIT-LICENSE

class String
  def starts_with?(substr)
    self[0...substr.size] == substr
  end

  def replace_end(old_str, new_str)
    s = old_str.size
    self[-s,s]=new_str
  end
end

class Githubify
  attr_accessor :input, :username
  attr_reader :errors, :project_name, :project_line

  def initialize
    @errors = []
  end

  def run
    return false unless valid?
    update_gemspec!
    store_gemspec!
    true
  end

  def report_errors
    errors.each do |error|
      $stderr.puts error
    end
    nil
  end

  def username
    @username ||= `git config github.user`.strip
  end

  private

  def gemspec
    @gemspec ||= File.read(input)
  end

  def output
    input_base = File.basename(input)
    output_base = "#{username}-#{input_base}"
    input.replace_end(input_base, output_base)
  end

  def project_line
    @project_line ||= project_line_match[0]
  end

  def project_line_match
    @project_line_match ||= gemspec.match(/s.name\s*=\s*['"]([^'"]+)['"]/)
  end

  def project_name
    @project_name ||= project_line_match[1]
  end

  def store_gemspec!
    File.open(output, 'w') {|f| f.puts(gemspec)}
  end

  def valid?
    errors.clear
    errors << 'No github.user defined!' if username.empty?
    errors << 'Already githubified this project' if project_name.starts_with?("#{username}-")
    errors.size == 0
  end

  def update_gemspec!
    new_name = "#{username}-#{project_name}"
    gemspec.sub!(project_line, project_line.sub(project_name, new_name))
    nil
  end
end

gh = Githubify.new
gh.input = File.expand_path(ARGV.shift)
gh.username = ARGV.shift
success = gh.run
gh.report_errors unless success