Fix git rpr

Signed-off-by: Emile Vauge <emile@vauge.com>

.github/rpr.sh

@@ -4,9 +4,9 @@
 
 set -e # stop on error
 
-usage="$(basename "$0") pr -- rebase a Pull Request against current branch"
+usage="$(basename "$0") pr remote/branch -- rebase a Pull Request against a remote branch"
 
-if [ "$#" -ne 1 ]; then
+if [ "$#" -ne 2 ]; then
     echo "Illegal number of parameters"
     echo "$usage" >&2
     exit 1
@@ -16,20 +16,19 @@ command -v jq >/dev/null 2>&1 || { echo "I require jq but it's not installed.  A
 
 set -x # echo on
 
-base=$(git rev-parse --abbrev-ref HEAD)
+initial=$(git rev-parse --abbrev-ref HEAD)
 pr=$1
+base=$2
 remote=$(curl -s https://api.github.com/repos/containous/traefik/pulls/$pr | jq -r .head.repo.owner.login)
 branch=$(curl -s https://api.github.com/repos/containous/traefik/pulls/$pr | jq -r .head.ref)
 
-git checkout $base
-
 git remote add $remote git@github.com:$remote/traefik.git
 git fetch $remote $branch
 git checkout -t $remote/$branch
-git rebase origin/$base
+git rebase $base
 git push -f $remote $branch
 
 # clean
-git checkout $base
+git checkout $initial
 git branch -D $branch
 git remote remove $remote