jpeg: support version format.

Library/Homebrew/test/test_versions.rb

@@ -243,6 +243,10 @@ class VersionParsingTests < Test::Unit::TestCase
     assert_version_detected '1.2.0-rc2', 'http://www.apache.org/dyn/closer.cgi?path=/cassandra/1.2.0/apache-cassandra-1.2.0-rc2-bin.tar.gz'
   end
 
+  def test_jpeg_style
+    assert_version_detected '8d', 'http://www.ijg.org/files/jpegsrc.v8d.tar.gz'
+  end
+
   # def test_version_ghc_style
   #   assert_version_detected '7.0.4', 'http://www.haskell.org/ghc/dist/7.0.4/ghc-7.0.4-x86_64-apple-darwin.tar.bz2'
   #   assert_version_detected '7.0.4', 'http://www.haskell.org/ghc/dist/7.0.4/ghc-7.0.4-i386-apple-darwin.tar.bz2'

Library/Homebrew/version.rb

@@ -183,6 +183,10 @@ class Version
     # e.g. http://mirrors.jenkins-ci.org/war/1.486/jenkins.war
     m = /\/(\d\.\d+)\//.match(spec.to_s)
     return m.captures.first unless m.nil?
+
+    # e.g. http://www.ijg.org/files/jpegsrc.v8d.tar.gz
+    m = /\.v(\d+[a-z]?)/.match(stem)
+    return m.captures.first unless m.nil?
   end
 
   # DSL for defining comparators