Initial version comparison implementation

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Library/Homebrew/test/test_versions.rb

@@ -11,6 +11,10 @@ module VersionAssertions
   def assert_version_nil url
     assert_nil Version.parse(url)
   end
+
+  def assert_comparison a, comparison, b
+    eval "assert Version.new(a) #{comparison} Version.new(b)"
+  end
 end
 
 class TestBadVersion < TestBall
@@ -21,7 +25,19 @@ class TestBadVersion < TestBall
   end
 end
 
-class VersionTests < Test::Unit::TestCase
+class VersionComparisonTests < Test::Unit::TestCase
+  include VersionAssertions
+
+  def test_version_comparisons
+    assert_comparison '0.1', '==', '0.1.0'
+    assert_comparison '0.1', '!=', '0.2'
+    assert_comparison '1.2.3', '>', '1.2.2'
+    assert_comparison '1.2.3-p34', '>', '1.2.3-p33'
+    assert_comparison '1.2.4', '<', '1.2.4.1'
+  end
+end
+
+class VersionParsingTests < Test::Unit::TestCase
   include VersionAssertions
 
   def test_pathname_version

Library/Homebrew/version.rb

@@ -6,12 +6,30 @@ class Version
     @version = val.to_s.strip
   end
 
+  def head?
+    @version == 'HEAD'
+  end
+
   def nums
     @version.scan(/\d+/).map { |d| d.to_i }
   end
 
   def <=>(other)
-    @version <=> other.version
+    return nil unless other.is_a? Version
+    return 0 if self.head? and other.head?
+    return 1 if self.head? and not other.head?
+    return -1 if not self.head? and other.head?
+    return 1 if other.nil?
+
+    snums = self.nums
+    onums = other.nums
+
+    count = [snums.length, onums.length].max
+
+    snums.fill(0, snums.length, count - snums.length)
+    onums.fill(0, onums.length, count - onums.length)
+
+    snums <=> onums
   end
 
   def to_s