On Windows XP SP3, using a precompiled binary from (73c24ae363] 2010-03-18), the following command fails unless a fossil repository has been opened in the current directory:

  fossil branch new BranchA 2848a7f6d9 -R ..\my.repo

  --> fossil: use --repository or -R to specify the repository database

The following succeeds:

  fossil open ..\my.repo

  --> ... checkout: e5f12d6eef...

  fossil branch new BranchA 2848a7f6d9 -R ..\my.repo

And correctly creates the new BranchA off basis 2848a7f6d9.  Also works (in the latter case) without the -R.