Added reading of base commit in pulls

          rm pup_v0.4.0_linux_amd64.zip

          BRANCH=$(curl https://github.com/uazo/bromite/branch_commits/$RTAG | ./pup -p li.branch:last-child a text{})

          if [ -z "${BRANCH}" ]; then

            BRANCH=$(cat a | ./pup -p li.branch:first-child a text{})

          fi

          if [ -z "${BRANCH}" ]; then

            echo "Impossible to recover the base commit"

            exit 1

          fi

          echo "BRANCH=$BRANCH" >> $GITHUB_ENV

      - name: Checkout 'uazo/bromite' ${{ env.BRANCH }}