create-pull-request: Assume remote branch from local branch
It is common to use the same remote branch name as the local branch
name. In this case, it would be nice not to have to specify the
remote branch name.
Make the -b argument optional and assume the remote branch is the same
name as the local branch. Print a NOTE to this effect so as not to
catch the user by surprise:
NOTE: Assuming remote branch 'notthere', use -b to override.
If the remote branch doesn't exist, a WARNING is displayed just as if
the user had used -b to specify a non-existent branch:
WARNING: Branch 'notthere' was not found on the contrib git tree.
Please check your remote and branch parameter before sending.
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
