ifchange.bat: --color option

* win32/ifchange.bat: added --color option for the compatibility
  with tool/ifchange.  do nothing right now.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62299 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

win32/ifchange.bat

@@ -4,6 +4,7 @@
 set timestamp=
 set keepsuffix=
 set empty=
+set color=auto
 :optloop
 for %%I in (%1) do set opt=%%~I
 if "%opt%" == "--timestamp" (
@@ -26,6 +27,14 @@ if "%opt%" == "--timestamp" (
     set empty=yes
     shift
     goto :optloop
+) else if "%opt%" == "--color" (
+    set color=always
+    shift
+    goto :optloop
+) else if "%opt:~0,8%" == "--color=" (
+    set color=%opt:~8%
+    shift
+    goto :optloop
 )
 if "%opt%" == "" goto :end