transport-helper: barf when user tries old:new
transport-helper: barf when user tries old:new

Otherwise with certain remote helpers (the ones that support 'export'),
the users will be pushing to the wrong branch:

  git push topic:master

Will push the topic branch, as if the user typed:

  git push topic

Signed-off-by: Felipe Contreras <de77a8b9cd239b204c19c52ed62e48ab47243362@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git