devtool: upgrade: provide a means to update the source branch
If you're upgrading a git recipe to a revision on a release branch
that's different to the branch for the current revision, then you'll
need to update the branch parameter in SRC_URI, so add a --srcbranch/-B
command-line parameter to let you do that easily. It handles both when
the branch is stated verbatim in the recipe, and when a reference to
another variable is used (a common convention is to use a SRCBRANCH
variable for this, though the code doesn't care what variable is used
if any).
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
