appliance: fix branch finding method from e16414e even Junio can be wrong

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
(cherry picked from commit bbaefb8e5def610a654fba907c8ec3f868416bdf)
Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>