ci: Schedule monthly build to catch regressions

Schedule monthly build to catch regressions in the build system during
times of no commit/merge activity.  Run build at 13:37 on the 14th of
each month to help reduce peak load.

See https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows#scheduled-events

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 661e8b7..3d83abb 100644 (file)
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -3,7 +3,16 @@
 # and attaching Windows and macOS builds, as well as the source archive.
 name: Quassel CI
 
-on: [ push, pull_request ]
+on:
+  push:
+  pull_request:
+  schedule:
+    # * is a special character in YAML so you have to quote this string
+    # Run at 13:37 on the 14th of every month (odd time to reduce load)
+    - cron: '37 13 14 * *'
+
+# Can't use simpler definition of [ push, pull_request, schedule ]
+# See https://www.jeffgeerling.com/blog/2020/running-github-actions-workflow-on-schedule-and-other-events
 
 defaults:
   run: