Add several improvements to GHA example

- "workflow_dispatch" so we can trigger manually
- "concurrency" so we avoid over-triggering when updating PRs/branches
- multi-line string in GITHUB_OUTPUT for better output and less flakiness

Author: tianon

scripts/github-actions/example-ci.yml

@@ -3,13 +3,18 @@ name: GitHub CI
 on:
   pull_request:
   push:
+  workflow_dispatch:
   schedule:
     - cron: 0 0 * * 0
 
 defaults:
   run:
     shell: 'bash -Eeuo pipefail -x {0}'
 
+concurrency:
+  group: ${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
 
   generate-jobs:
@@ -24,8 +29,11 @@ jobs:
         name: Generate Jobs
         run: |
           strategy="$("$BASHBREW_SCRIPTS/github-actions/generate.sh")"
-          echo "strategy=$strategy" >> "$GITHUB_OUTPUT"
-          jq . <<<"$strategy" # sanity check / debugging aid
+
+          EOF="EOF-$RANDOM-$RANDOM-$RANDOM"
+          echo "strategy<<$EOF" >> "$GITHUB_OUTPUT"
+          jq <<<"$strategy" . | tee -a "$GITHUB_OUTPUT"
+          echo "$EOF" >> "$GITHUB_OUTPUT"
 
   test:
     needs: generate-jobs