fix env var handling

.drone.yml

@@ -7,7 +7,7 @@ steps:
     image: xoxys/rpmbuild
     pull: always
     environment:
-      CUPSRELEASE: "2.2.10"
+      CUPSRELEASE: "${DRONE_TAG##v:-2.2.10}"
     commands:
       - wget https://github.com/apple/cups/releases/download/v$CUPSRELEASE/cups-$CUPSRELEASE-source.tar.gz
       - mkdir ./rpms
@@ -22,8 +22,6 @@ steps:
     pull: always
     commands:
       - apk add --no-cache coreutils
-      # exclude files
-      # - sha256sum -b files/!(*.out) > CHECKSUMFILE
       - sha256sum -b rpms/x86_64/* > sha256sum.txt
     when:
       event: