Question

~/www> git branch --track live origin/master
fatal: Not a valid object name: 'origin/master'.
~/www> git remote
origin
~/www> git branch
* master
  test_branch
  working_branch

I also tried creating a tracking branch with:

git branch live
git branch --set-upstream live origin/master

but I got the same error

Answer 1

$ git branch -r
  origin/1.x
  origin/1.x@60
  origin/1.x@63
  origin/HEAD -> origin/master
  origin/master

$ git branch --track live origin/blah
fatal: Not a valid object name: 'origin/blah'.

As has been suggested you can only track a remote if it has been added. Perhaps add the remote like this

$ git remote add upstream git://github.com/svnpenn/rtmpdump.git

$ git fetch upstream

Example