From: Marc Heiler <shevegen@...>
Date: 2011-07-17T03:55:14+09:00
Subject: Re: Anyone interested in a Package Manager in Ruby?

To Brian,

> Have you compared your scripts against homebrew?

>   http://mxcl.github.com/homebrew/

I had some time to look at homebrew.

First, at #homebrew. Well ... 42 people ... no reply to a question I 
asked.

:(

So I went to the site and noticed they used Github. This is GREAT.

They have a structure with about 1600 formulas. A formula is a ruby file 
which looks like this:

  https://github.com/mxcl/homebrew/blob/master/Library/Formula/simh.rb

It uses methods to convey the information:

  url 'http://simh.trailing-edge.com/sources/simhv38-1.zip'
  version '3.8-1'
  homepage 'http://simh.trailing-edge.com/'
  md5 'e15f65a82e21ea49e14b438326d93d5c'

url method probably points to the URL of the program where you can 
download it ... homepage provides some information ... md5 the md5sum I 
suppose... version may be something internal, or whatever. The -1 part 
at the version is probably a revision number.

I am unhappy with the choice to store the data in pure ruby though.

I feel the data should be ideally decoupled from any language.

Take 
https://github.com/mxcl/homebrew/blob/master/Library/Formula/a2ps.rb

You have boilerplate code there:

  require 'formula'

  class A2ps < Formula

Perhaps I am too stringent on purity but to me it feels like a 
suboptimal solution. The same could be achieved by a bit of 
metaprogramming.

The class name derives from the file name.rb anyway ...


The main script seems to be at:

  https://github.com/mxcl/homebrew/blob/master/Library/Homebrew/formula.rb

There is another thing I don't understand.

This could work on *nix systems just as easily. Just compile into a 
standalone directory, register the files there, and symlink or copy them 
into the FHS directory try. Why does homebrew want to be known as only 
Mac OS usable? I don't quite understand that.

There are some interesting strategies used in formula.rb though.

For instance, they bundle different download strategies together:


  VCS_SYMBOLS = {
    :bzr => BazaarDownloadStrategy,
    :curl => CurlDownloadStrategy,
    :cvs => CVSDownloadStrategy,
    :git => GitDownloadStrategy,
    :hg => MercurialDownloadStrategy,
    :nounzip => NoUnzipCurlDownloadStrategy,
    :post => CurlPostDownloadStrategy,
    :svn => SubversionDownloadStrategy,
  }


  def initialize(url, specs = nil)
    unless specs.nil?
      # Get download strategy hint, if any
      @using = specs.delete :using

    detected = VCS_SYMBOLS[@using]

I found this nice. Never thought of a fairly complete download strategy 
yet, especially not :post or :nounzip haha :D

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