discourse-release: announce a given tag, for releases made by the job's own token

Gitea starts no workflow for events caused by the Actions bot, so a release
created with GITHUB_TOKEN never fires 'on: release'. With 'tag:' the action
fetches that release itself; drafts are skipped.

discourse-release/action.yml

@@ -11,6 +11,14 @@ inputs:
     description: optional Discord webhook URL; when set, the announcement is also posted there
     required: false
     default: ""
+  tag:
+    description: >-
+      announce the release with this tag instead of the triggering release
+      event. Needed in a workflow that creates its release with the job's own
+      token: Gitea does not start workflows for events the Actions bot causes,
+      so `on: release` never fires for those releases.
+    required: false
+    default: ""
   forum:
     description: forum base URL
     required: false
@@ -25,6 +33,8 @@ runs:
         FORUM: ${{ inputs.forum }}
         REPO: ${{ github.repository }}
         EVENT_PATH: ${{ github.event_path }}
+        TAG: ${{ inputs.tag }}
+        GITEA_TOKEN: ${{ github.token }}
         ACTION_PATH: ${{ github.action_path }}
         MAP: ${{ github.action_path }}/release-map.json
       run: |

discourse-release/announce.sh

@@ -10,6 +10,19 @@ if [ -z "$category_path" ]; then
   exit 1
 fi
 
+if [ -n "${TAG:-}" ]; then
+  # Called with a tag (a release made by the job's own token): fetch it and
+  # treat it as the event, so everything below is the same either way.
+  base="${CI_SERVER_INTERNAL:-$GITHUB_SERVER_URL}"
+  EVENT_PATH=$(mktemp)
+  curl -fsS -H "Authorization: token $GITEA_TOKEN" "$base/api/v1/repos/$REPO/releases/tags/$TAG" |
+    jq '{release: .}' > "$EVENT_PATH"
+fi
+if [ "$(jq -r '.release.draft // false' "$EVENT_PATH")" = true ]; then
+  echo "release is a draft; not announcing"
+  exit 0
+fi
+
 tag=$(jq -r '.release.tag_name' "$EVENT_PATH")
 # The category id, looked up anonymously (the category is public); the
 # release-bot key is scoped to creating posts and nothing else.