Extracted capistrano multiconfig from deployment project

Author: ayanko

.gitignore

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+*.gem
+.bundle
+Gemfile.lock
+pkg/*

Gemfile

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+source "http://rubygems.org"

README.md

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+# capistrano-multiconfig
+
+## Description
+
+Capistrano extension that allows to use multiple configurations.
+
+Multiconfig extension is similar to [multistage](https://github.com/capistrano/capistrano-ext) extenstion.
+But it's not only about 'stage' configurations. It's about any configuration that you may need.
+Extension recursively builds configuration list from configuration root directory.
+Each configuration loads recursively configuration from it namespace files and own configuration file.
+
+## Usage
+
+Install gem
+
+    $ gem install capistrano-multistage
+
+
+Add to `Capfile`
+
+    set :config, 'path/to/your/configurations'
+    require 'capistrano/multiconfig'
+
+## Example
+
+Assume we need next configurations:
+
+* services:billing:production
+* services:billing:qa
+* blog:production
+* blog:staging
+* dev:wiki
+
+Choose configuration root directory for example `config/deploy`
+
+Create configuration files:
+
+    config/deploy/services/billing/production.rb
+    config/deploy/services/billing/qa.rb
+    config/deploy/blog/production.rb
+    config/deploy/blog/staging.rb
+    config/deploy/dev/wiki.rb
+
+Add to `Capfile`:
+
+    set :config_root, 'config/deploy'
+    require 'capistrano/multiconfig'
+
+Put related capistrano configuration to each file according to file meaning.
+
+Check tasks:
+
+    $ cap -T
+    cap services:billing:production # Load services:billing:production configuration
+    cap services:billing:qa         # Load services:billing:qa configuration
+    cap blog:production             # Load blog:production configuration
+    cap blog:staging                # Load blog:staging configuration
+    cap wiki                        # Load wiki configuration
+    cap invoke                      # Invoke a single command on the remote servers.
+    cap shell                       # Begin an interactive Capistrano session.
+
+Let's try to run task without specified configuration:
+
+    $ cap shell
+    triggering start callbacks for `shell'
+      * executing `multiconfig:ensure'
+    No configuration specified. Please specify one of:
+      * wiki:production
+      * wiki:staging
+      * blog:production
+      * blog:staging
+    (e.g. `cap wiki:production shell')
+
+
+So we must provide configuration as first task:
+
+    $ cap services:billing:qa shell
+
+## Configuration Loading
+
+Configuration task loads not only configuration associated with it filename.
+It also recursively load configurations from all namespaces.
+
+For example for *:config_root* `config/deploy` task `cap apps/blog/qa.rb` loads with **order** next configuration files (if they exist):
+
+* config/deploy/apps.rb
+* config/deploy/apps/blog.rb
+* config/deploy/apps/blog/qa.rb
+
+So it's easy to put shared configuration.

Rakefile

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+require "bundler/gem_tasks"

capistrano-multiconfig.gemspec

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+# -*- encoding: utf-8 -*-
+$:.push File.expand_path("../lib", __FILE__)
+
+Gem::Specification.new do |s|
+  s.name        = "capistrano-multiconfig"
+  s.version     = "0.0.1"
+  s.authors     = ["Andriy Yanko"]
+  s.email       = ["[email protected]"]
+  s.homepage    = "https://github.com/railsware/multiconfig"
+  s.summary     = %q{Capistrano extension that allows to use multiple configurations}
+  s.description = %q{
+Multiconfig extension is similar to [multistage](https://github.com/capistrano/capistrano-ext) extenstion.
+But it's not only about 'stage' configurations. It's about any configuration that you may need.
+Extension recursively builds configuration list from configuration root directory.
+Each configuration loads recursively configuration from namespace files and own configuration file.
+  }
+
+  s.rubyforge_project = "capistrano-multiconfig"
+
+  s.files         = `git ls-files`.split("\n")
+  s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
+  s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
+  s.require_paths = ["lib"]
+
+  s.add_runtime_dependency "capistrano", ">=2.5.5"
+end

lib/capistrano/multiconfig.rb

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+require 'capistrano/multiconfig/configurations'
+require 'capistrano/multiconfig/ensure'

lib/capistrano/multiconfig/configurations.rb

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+Capistrano::Configuration.instance.load do
+  # configurations root directory
+  config_root = File.expand_path(fetch(:config_root, "config/deploy"))
+
+  # list of configurations files
+  config_files = Dir["#{config_root}/**/*.rb"]
+
+  # remove configuration file if it's part of another configuration
+  config_files.reject! do |config_file|
+    config_dir = config_file.gsub(/\.rb$/, '/')
+    config_files.any? { |file| file[0, config_dir.size] == config_dir }
+  end
+
+  # build configuration names list
+  config_names = config_files.map do |config_file|
+    config_file.sub("#{config_root}/", '').sub(/\.rb$/, '').gsub('/', ':')
+  end
+
+  # ensure that configuration segments don't override any method, task or namespace
+  config_names.each do |config_name|
+    config_name.split(':').each do |segment|
+      if all_methods.any? { |m| m == segment }
+        raise ArgumentError,
+          "Config task #{config_name} name overrides #{segment.inspect} (method|task|namespace)"
+      end
+    end
+  end
+
+  # create configuration task for each configuration name
+  config_names.each do |config_name|
+    segments = config_name.split(':')
+    namespace_names = segments[0, segments.size - 1]
+    task_name = segments.last
+
+    # create configuration task block
+    block = lambda do
+      desc "Load #{config_name} configuration"
+      task(task_name) do
+        # set configuration name as :config_name variable
+        self.set(:config_name, config_name)
+
+        # recursively load configurations
+        segments.size.times do |i|
+          path = ([config_root] + segments[0..i]).join('/') + '.rb'
+          self.load(path) if File.exists?(path)
+        end
+      end
+    end
+
+    # wrap task block into namespace blocks
+    block = namespace_names.reverse.inject(block) do |child, name|
+      lambda do
+        namespace(name, &child)
+      end
+    end
+
+    # create configuration task
+    block.call
+  end
+
+  # set configuration names list
+  set(:config_names, config_names)
+end

lib/capistrano/multiconfig/ensure.rb

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+Capistrano::Configuration.instance.load do
+  namespace :multiconfig do
+    desc "[internal] Ensure that a configuration has been selected"
+    task :ensure do
+      unless exists?(:config_name)
+        puts "No configuration specified. Please specify one of:"
+        config_names.each { |name| puts "  * #{name}" }
+        puts "(e.g. `cap #{config_names.first} #{ARGV.last}')"
+        abort
+      end
+    end
+  end
+
+  on :start, 'multiconfig:ensure', :except => config_names
+end