CI: build & publish only when tag

.woodpecker.yml

@@ -12,6 +12,8 @@ pipeline:
       - ./tests.sh --quiet
   build:
     image: debian
+    when:
+      tag: *
     commands:
       - DEBIAN_FRONTEND=noninteractive apt-get -qq update < /dev/null > /dev/null
       - DEBIAN_FRONTEND=noninteractive apt-get -y -qq upgrade < /dev/null > /dev/null
@@ -20,6 +22,8 @@ pipeline:
       - rm -fr deb_dist/python3-mylib-*
   publish:
     image: plugins/gitea-release
+    when:
+      tag: *
     settings:
       api_key:
         from_secret: gitea_token