New patch implementation and DSL

This commit introduces a new patch implementation that supports
checksums and caching.

Patches are declared in blocks:

  patch do
    url ...
    sha1 ...
  end

A strip level of -p1 is assumed. It can be overridden using a symbol
argument:

  patch :p0 do
    url ...
    sha1 ...
  end

Patches can be declared in stable, devel, and head blocks. This form is
preferred over using conditionals.

  stable do
    # ...

    patch do
      url ...
      sha1 ...
    end
  end

Embedded (__END__) patches are declared like so:

  patch :DATA
  patch :p0, :DATA

Patches can also be embedded by passing a string. This makes it possible
to provide multiple embedded patches while making only some of them
conditional.

  patch :p0, "..."

7 files changed, 180 insertions, 20 deletions

diff --git a/Library/Contributions/example-formula.rb b/Library/Contributions/example-formula.rb
index 305ffd187..fb54b2ad1 100644
--- a/Library/Contributions/example-formula.rb
+++ b/Library/Contributions/example-formula.rb
@@ -213,26 +213,36 @@ class ExampleFormula < Formula
 
   ## Patches
 
-  # Optionally define a `patches` method returning `DATA` and/or a string with
-  # the url to a patch or a list thereof.
-  def patches
-    # DATA is the embedded diff that comes after __END__ in this file!
-    # In this example we only need the patch for older clang than 425:
-    DATA unless MacOS.clang_build_version >= 425
+  # External patches can be declared using resource-style blocks.
+  patch do
+    url "https://example.com/example_patch.diff"
+    sha1 "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"
   end
 
-  # More than the one embedded patch? Use a dict with keys :p0, :p1 and/or
-  # p2: as you need, for example:
-  def patches
-    {:p0 => [
-      'https://trac.macports.org/export/yeah/we/often/steal/a/patch.diff',
-      'https://github.com/example/foobar/commit/d46a8c6265c4c741aaae2b807a41ea31bc097052.diff',
-      DATA ],
-     # For gists, please use the link to a specific hash, so nobody can change it unnoticed.
-     :p2 => ['https://raw.github.com/gist/4010022/ab0697dc87a40e65011e2192439609c17578c5be/tags.patch']
-    }
+  # A strip level of -p1 is assumed. It can be overridden using a symbol
+  # argument:
+  patch :p0 do
+    url "https://example.com/example_patch.diff"
+    sha1 "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"
   end
 
+  # Patches can be declared in stable, devel, and head blocks. This form is
+  # preferred over using conditionals.
+  stable do
+    patch do
+      url "https://example.com/example_patch.diff"
+      sha1 "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"
+    end
+  end
+
+  # Embedded (__END__) patches are declared like so:
+  patch :DATA
+  patch :p0, :DATA
+
+  # Patches can also be embedded by passing a string. This makes it possible
+  # to provide multiple embedded patches while making only some of them
+  # conditional.
+  patch :p0, "..."
 
   ## The install method.
 
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 71e2a730c..57eb2ab4c 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -743,6 +743,10 @@ class Formula
       specs.each { |spec| spec.option(name, description) }
     end
 
+    def patch strip=:p1, io=nil, &block
+      specs.each { |spec| spec.patch(strip, io, &block) }
+    end
+
     def plist_options options
       @plist_startup = options[:startup]
       @plist_manual = options[:manual]
diff --git a/Library/Homebrew/patch.rb b/Library/Homebrew/patch.rb
new file mode 100644
index 000000000..a4616eee6
--- /dev/null
+++ b/Library/Homebrew/patch.rb
@@ -0,0 +1,82 @@
+require 'resource'
+require 'stringio'
+
+class Patch
+  def self.create(strip, io=nil, &block)
+    case strip ||= :p1
+    when :DATA, IO, StringIO
+      IOPatch.new(strip, :p1)
+    when String
+      IOPatch.new(StringIO.new(strip), :p1)
+    when Symbol
+      case io
+      when :DATA, IO, StringIO
+        IOPatch.new(io, strip)
+      when String
+        IOPatch.new(StringIO.new(io), strip)
+      else
+        ExternalPatch.new(strip, &block)
+      end
+    else
+      raise ArgumentError, "unexpected value #{strip.inspect} for strip"
+    end
+  end
+
+  attr_reader :whence
+
+  def external?
+    whence == :resource
+  end
+end
+
+class IOPatch < Patch
+  attr_writer :owner
+  attr_reader :strip
+
+  def initialize(io, strip)
+    @io     = io
+    @strip  = strip
+    @whence = :io
+  end
+
+  def apply
+    @io = DATA if @io == :DATA
+    data = @io.read
+    data.gsub!("HOMEBREW_PREFIX", HOMEBREW_PREFIX)
+    IO.popen("/usr/bin/patch -g 0 -f -#{strip}", "w") { |p| p.write(data) }
+    raise ErrorDuringExecution, "Applying DATA patch failed" unless $?.success?
+  ensure
+    # IO and StringIO cannot be marshaled, so remove the reference
+    # in case we are indirectly referenced by an exception later.
+    @io = nil
+  end
+end
+
+class ExternalPatch < Patch
+  attr_reader :resource, :strip
+
+  def initialize(strip, &block)
+    @strip    = strip
+    @resource = Resource.new(&block)
+    @whence   = :resource
+  end
+
+  def url
+    resource.url
+  end
+
+  def owner= owner
+    resource.owner   = owner
+    resource.name    = "patch-#{resource.checksum}"
+    resource.version = owner.version
+  end
+
+  def apply
+    dir = Pathname.pwd
+    resource.unpack do
+      # Assumption: the only file in the staging directory is the patch
+      patchfile = Pathname.pwd.children.first
+      safe_system "/usr/bin/patch", "-g", "0", "-f", "-d", dir, "-#{strip}", "-i", patchfile
+    end
+  end
+end
diff --git a/Library/Homebrew/resource.rb b/Library/Homebrew/resource.rb
index d1f0b91b4..a9380db88 100644
--- a/Library/Homebrew/resource.rb
+++ b/Library/Homebrew/resource.rb
@@ -8,13 +8,12 @@ require 'version'
 class Resource
   include FileUtils
 
-  attr_reader :name
   attr_reader :checksum, :mirrors, :specs, :using
   attr_writer :url, :checksum, :version
 
   # Formula name must be set after the DSL, as we have no access to the
   # formula name before initialization of the formula
-  attr_accessor :owner
+  attr_accessor :name, :owner
 
   def initialize name=nil, &block
     @name = name
diff --git a/Library/Homebrew/software_spec.rb b/Library/Homebrew/software_spec.rb
index 43969b2fa..0349dd3dd 100644
--- a/Library/Homebrew/software_spec.rb
+++ b/Library/Homebrew/software_spec.rb
@@ -5,12 +5,13 @@ require 'version'
 require 'build_options'
 require 'dependency_collector'
 require 'bottles'
+require 'patch'
 
 class SoftwareSpec
   extend Forwardable
 
-  attr_reader :name
-  attr_reader :build, :resources, :owner
+  attr_reader :name, :owner
+  attr_reader :build, :resources, :patches
   attr_reader :dependency_collector
   attr_reader :bottle_specification
 
@@ -25,6 +26,7 @@ class SoftwareSpec
     @build = BuildOptions.new(ARGV.options_only)
     @dependency_collector = DependencyCollector.new
     @bottle_specification = BottleSpecification.new
+    @patches = []
   end
 
   def owner= owner
@@ -35,6 +37,7 @@ class SoftwareSpec
       r.owner     = self
       r.version ||= version
     end
+    patches.each { |p| p.owner = self }
   end
 
   def url val=nil, specs={}
@@ -84,6 +87,10 @@ class SoftwareSpec
   def requirements
     dependency_collector.requirements
   end
+
+  def patch strip=:p1, io=nil, &block
+    patches << Patch.create(strip, io, &block)
+  end
 end
 
 class HeadSoftwareSpec < SoftwareSpec
diff --git a/Library/Homebrew/test/test_patch.rb b/Library/Homebrew/test/test_patch.rb
new file mode 100644
index 000000000..1cc1ac7af
--- /dev/null
+++ b/Library/Homebrew/test/test_patch.rb
@@ -0,0 +1,52 @@
+require 'testing_env'
+require 'patch'
+
+class PatchTests < Test::Unit::TestCase
+  def test_create_simple
+    patch = Patch.create(:p2)
+    assert_kind_of ExternalPatch, patch
+    assert patch.external?
+    assert_equal :p2, patch.strip
+  end
+
+  def test_create_io
+    patch = Patch.create(:p0, StringIO.new("foo"))
+    assert_kind_of IOPatch, patch
+    assert !patch.external?
+    assert_equal :p0, patch.strip
+  end
+
+  def test_create_io_without_strip
+    patch = Patch.create(StringIO.new("foo"))
+    assert_kind_of IOPatch, patch
+    assert_equal :p1, patch.strip
+  end
+
+  def test_create_string
+    patch = Patch.create(:p0, "foo")
+    assert_kind_of IOPatch, patch
+    assert_equal :p0, patch.strip
+  end
+
+  def test_create_string_without_strip
+    patch = Patch.create("foo")
+    assert_kind_of IOPatch, patch
+    assert_equal :p1, patch.strip
+  end
+
+  def test_create_DATA
+    patch = Patch.create(:p0, :DATA)
+    assert_kind_of IOPatch, patch
+    assert_equal :p0, patch.strip
+  end
+
+  def test_create_DATA_without_strip
+    patch = Patch.create(:DATA)
+    assert_kind_of IOPatch, patch
+    assert_equal :p1, patch.strip
+  end
+
+  def test_raises_for_unknown_values
+    assert_raises(ArgumentError) { Patch.create(Object.new) }
+  end
+end
diff --git a/Library/Homebrew/test/test_software_spec.rb b/Library/Homebrew/test/test_software_spec.rb
index c35294320..7c9fb8720 100644
--- a/Library/Homebrew/test/test_software_spec.rb
+++ b/Library/Homebrew/test/test_software_spec.rb
@@ -80,6 +80,12 @@ class SoftwareSpecTests < Test::Unit::TestCase
     @spec.depends_on('foo' => :optional)
     assert_equal 'blah', @spec.build.first.description
   end
+
+  def test_patch
+    @spec.patch :p1, :DATA
+    assert_equal 1, @spec.patches.length
+    assert_equal :p1, @spec.patches.first.strip
+  end
 end
 
 class HeadSoftwareSpecTests < Test::Unit::TestCase