three rake tasks for jekyll - scaffold new post, open last edited post, and open latest post.

post_editor.rb

class PostEditor
  FILENAME_MSG = '(you can leave this blank)'
  POST_TEMPLATE = <<-Template
---
title: 
_filename_: #{FILENAME_MSG}
categories:
-
tags:
-
date: #{Time.now.strftime('%Y-%m-%d %H:%M')}
layout: post
comments: true
---

  Template

  include Jekyll::Convertible

  def initialize
    assert_editor
  end
  attr_accessor :data, :content

  def create_post(ext = '.markdown')
    FileUtils.mkdir_p('_posts', verbose: true)

    Tempfile.open(['jekyll_new_post_', ext]) do |tf|
      tf.print POST_TEMPLATE
      tf.close
      execute_editor(tf.path)
      save_new_post(tf)
    end
  end

  def edit_last_post
    newest_post = Dir.glob('_posts/*').
      select {|x| File.file?(x) && /\A\./ !~ x }.
      sort_by {|x| File.mtime(x) }.last

    execute_editor(newest_post)
  end

  def edit_latest_post
    latest_post = Dir.glob('_posts/*').
      select {|x| File.file?(x) && /\A\./ !~ x }.
      sort_by {|x| File.basename(x) }.last

    execute_editor(latest_post)
  end

  def site
    nil
  end

  def converter
    nil
  end

  private

  def assert_editor
    raise 'set EDITOR!' unless ENV['EDITOR']
  end

  def execute_editor(path)
    raise 'no file to edit' unless path

    system ENV['EDITOR'], path
    raise "#{ENV['EDITOR']} failed" unless $?.success?
  end

  def save_new_post(tmpfile)
    read_yaml(*File.split(tmpfile.path))

    %w(tags categories).each do |key|
      data[key].compact!
    end

    time = data['date']
    unless time.is_a?(Time)
      time = Time.parse(time) rescue Time.now
    end

    filename = (data.delete('_filename_') || '').strip
    if filename == FILENAME_MSG.strip || filename.empty?
      filename = (data['title'] || '').strip
    end

    filename_base = File.join(
      '_posts',
      time.strftime('%Y-%m-%d-') +
      filename.gsub(/[\s\W]/, '-'))

    ext = File.extname(tmpfile.path)
    num = 1
    begin
      path = filename_base +
        (num == 1 ? '' : "-#{num}") + ext

      File.open(path, File::RDWR|File::CREAT|File::EXCL) do |io|
        io.print YAML.dump(data)
        io.puts '---'
        io.puts self.content.chomp
      end
      return path

    rescue Errno::EEXIST
      num += 1
      if num == 10
        raise "new post can not be saved correctly\ncheck filename or title of your new post"
      end
      retry
    end

  rescue Exception
    msg = "your content saved in "
    begin
      expath =
        tmpfile.path[0, tmpfile.path.size - ext.size] +
        Time.now.strftime('_%Y%m%d_%H%M%S') + ext
      FileUtils.mv(tmpfile.path, expath)
      msg << expath
    rescue Exception
      ObjectSpace.undefine_finalizer(tmpfile) # XXX: これで大丈夫?
      msg << tmpfile.path
    end
    raise $!.class, "#{$!.message}\n#{msg}", $!.backtrace
  end
end

Rakefile

require 'rubygems'
require 'fileutils'
require 'open-uri'
require 'pathname'

task :bundler do
  require 'bundler/setup'
  Bundler.require(:default)
  require 'jekyll'
  require './_libs/post_editor'
end

desc 'Write a new post'
task :new => [:bundler] do
  path = PostEditor.new.create_post
  Rake.rake_output_message "content saved in #{path}\n'rake last' can open the file"
end

desc 'Open the last edited post'
task :last => [:bundler] do
  PostEditor.new.edit_last_post
end

desc 'Open the newest post'
task :latest => [:bundler] do
  PostEditor.new.edit_latest_post
end