add pushurl's to sources

sources.cfg

 [buildout]
 extends = http://svn.zope.org/repos/main/zopetoolkit/trunk/ztk-sources.cfg
+
+[remotes]
 svn-zope-org = ^
 github = git://github.com/zopefoundation
+github_push = git@github.com:zopefoundation
 
 [sources]
 # Zope2-specific
-AccessControl = git ${buildout:github}/AccessControl
-Acquisition = git ${buildout:github}/Acquisition
-DateTime = git ${buildout:github}/DateTime
-DocumentTemplate = git ${buildout:github}/DocumentTemplate
-ExtensionClass = git ${buildout:github}/ExtensionClass
-initgroups = git ${buildout:github}/initgroups
-Missing = git ${buildout:github}/Missing
-MultiMapping = git ${buildout:github}/MultiMapping
-nt_svcutils = git ${buildout:github}/nt_svcutils
-Persistence = git ${buildout:github}/Persistence
-Products.OFSP = git ${buildout:github}/Products.OFSP
-Products.ZCatalog = git ${buildout:github}/Products.ZCatalog
-Products.ZCTextIndex = git ${buildout:github}/Products.ZCTextIndex
-Record = git ${buildout:github}/Record
-tempstorage = git ${buildout:github}/tempstorage
-zExceptions = git ${buildout:github}/zExceptions
-zLOG = svn ${buildout:svn-zope-org}/zLOG/trunk
-ZopeUndo = git ${buildout:github}/ZopeUndo
+AccessControl = git ${remotes:github}/AccessControl pushurl=${remotes:github_push}/AccessControl
+Acquisition = git ${remotes:github}/Acquisition pushurl=${remotes:github_push}/Acquisition
+DateTime = git ${remotes:github}/DateTime pushurl=${remotes:github_push}/DateTime
+DocumentTemplate = git ${remotes:github}/DocumentTemplate pushurl=${remotes:github_push}/DocumentTemplate
+ExtensionClass = git ${remotes:github}/ExtensionClass pushurl=${remotes:github_push}/ExtensionClass
+initgroups = git ${remotes:github}/initgroups pushurl=${remotes:github_push}/initgroups
+Missing = git ${remotes:github}/Missing pushurl=${remotes:github_push}/Missing
+MultiMapping = git ${remotes:github}/MultiMapping pushurl=${remotes:github_push}/MultiMapping
+nt_svcutils = git ${remotes:github}/nt_svcutils pushurl=${remotes:github_push}/nt_svcutils
+Persistence = git ${remotes:github}/Persistence pushurl=${remotes:github_push}/Persistence
+Products.OFSP = git ${remotes:github}/Products.OFSP pushurl=${remotes:github_push}/Products.OFSP
+Products.ZCatalog = git ${remotes:github}/Products.ZCatalog pushurl=${remotes:github_push}/Products.ZCatalog
+Products.ZCTextIndex = git ${remotes:github}/Products.ZCTextIndex pushurl=${remotes:github_push}/Products.ZCTextIndex
+Record = git ${remotes:github}/Record pushurl=${remotes:github_push}/Record
+tempstorage = git ${remotes:github}/tempstorage pushurl=${remotes:github_push}/tempstorage
+zExceptions = git ${remotes:github}/zExceptions pushurl=${remotes:github_push}/zExceptions
+zLOG = svn ${remotes:svn-zope-org}/zLOG/trunk
+ZopeUndo = git ${remotes:github}/ZopeUndo pushurl=${remotes:github_push}/ZopeUndo
 
 # Deprecated / CMF dependencies
-Products.BTreeFolder2 = git ${buildout:github}/Products.BTreeFolder2
-Products.ExternalMethod = git ${buildout:github}/Products.ExternalMethod
-Products.MailHost = svn ${buildout:svn-zope-org}/Products.MailHost/trunk
-Products.PythonScripts = git ${buildout:github}/Products.PythonScripts
-Products.StandardCacheManagers = git ${buildout:github}/Products.StandardCacheManagers
+Products.BTreeFolder2 = git ${remotes:github}/Products.BTreeFolder2 pushurl=${remotes:github_push}/Products.BTreeFolder2
+Products.ExternalMethod = git ${remotes:github}/Products.ExternalMethod pushurl=${remotes:github_push}/Products.ExternalMethod
+Products.MailHost = svn ${remotes:svn-zope-org}/Products.MailHost/trunk
+Products.PythonScripts = git ${remotes:github}/Products.PythonScripts pushurl=${remotes:github_push}/Products.PythonScripts
+Products.StandardCacheManagers = git ${remotes:github}/Products.StandardCacheManagers pushurl=${remotes:github_push}/Products.StandardCacheManagers