changelog and benchmark for #502

Using require_relative instead of require results in a roughly 12%
improvement in the time it takes to load rspec-core's own lib files

Changelog.md

@@ -9,6 +9,7 @@ Enhancments
     * deletes obsolete files (on confirmation) 
     * merged with and deprecates `--configure` command, which generated
       `.rspec`
+* use `require_relative` when available (Ian Leitch)
 
 ### 2.8.0.rc1 / 2011-11-06
 

benchmarks/require_relative_v_require.rb

@@ -0,0 +1,51 @@
+require 'benchmark'
+
+n = 20
+
+Benchmark.benchmark do |bm|
+  3.times.each do
+    bm.report do
+      n.times do
+        pid = fork do
+          require 'rspec/core'
+        end
+        Process.wait(pid)
+      end
+    end
+  end
+end
+
+# ###################################
+# Ruby 1.9.3 - 3 x 20
+# require
+# $ bundle exec ruby benchmarks/require_relative_v_require.rb 
+#    0.000000   0.020000   2.540000 (  2.568784)
+#    0.000000   0.010000   2.550000 (  2.580621)
+#    0.000000   0.020000   2.510000 (  2.548631)
+#
+# require_relative
+# $ bundle exec ruby benchmarks/require_relative_v_require.rb 
+#    0.000000   0.010000   2.220000 (  2.288229)
+#    0.000000   0.010000   2.250000 (  2.289886)
+#    0.000000   0.020000   2.260000 (  2.296639)
+#
+# roughly 12% improvement
+#
+# ###################################
+#
+# Ruby 1.8.7 - 3 x 20
+# before change (using require, but no conditional)
+# $ bundle exec ruby benchmarks/require_relative_v_require.rb 
+#   0.000000   0.010000   1.210000 (  1.242291)
+#   0.000000   0.010000   1.230000 (  1.259518)
+#   0.000000   0.010000   1.230000 (  1.250333)
+#
+# after change (still using require, but adding conditional)
+# $ bundle exec ruby benchmarks/require_relative_v_require.rb 
+#   0.000000   0.010000   1.200000 (  1.227249)
+#   0.000000   0.010000   1.230000 (  1.257012)
+#   0.000000   0.010000   1.230000 (  1.259278)
+#
+# virtually no penalty
+#
+# ###################################