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, "..."

1 files changed, 82 insertions, 0 deletions

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