Create update.yml

- runs on a frequent schedule
- checks out LoopWorkspace `main`
- compares and syncs with LoopKit/LoopWorkspace (unless owner = LoopKit)
- keepalive action adds empty commits to LoopKit/LoopWorkspace `main` after `time_elapsed` days to to avoid inactivation of scheduled workflows, when these updates are passed on to forks (only if owner = LoopKit)
- launches build_loop.yml workflow on forks to sync and build if new commits are found (unless owner = LoopKit)

Author: bjornoleh

.github/workflows/update.yml

@@ -0,0 +1,75 @@
+name: 'Auto-update'
+
+on:
+  schedule:
+    - cron:  '0 7 * * 1,4'
+    # scheduled at 07:00 every Monday and Thursday
+
+  workflow_dispatch:  # click the button on Github repo!
+
+env:
+  UPSTREAM_REPO: LoopKit/LoopWorkspace
+  UPSTREAM_BRANCH: main
+  TARGET_BRANCH: main
+
+jobs:
+  check_latest_from_upstream:
+    runs-on: ubuntu-latest
+    name: Check latest commits from upstream repo
+    outputs: 
+      NEW_COMMITS: ${{ steps.sync.outputs.has_new_commits }}
+
+    steps:
+    # REQUIRED step
+    # Step 1: run a standard checkout action, provided by github
+    - name: Checkout target repo
+      uses: actions/checkout@v3
+      with:
+        # optional: set the branch to checkout,
+        # sync action checks out your 'target_sync_branch' anyway
+        #submodules: recursive 
+        ref: ${{ env.TARGET_BRANCH }}
+
+    # REQUIRED step
+    # Step 2: run the sync action
+    - name: Sync upstream changes
+      if: (github.repository_owner != 'LoopKit')
+      id: sync
+      uses: aormsby/[email protected]
+      with:
+        target_sync_branch: ${{ env.TARGET_BRANCH }}
+        #target_branch_checkout_args: --recurse-submodules
+        shallow_since: 6 months ago
+        # REQUIRED 'target_repo_token' exactly like this!
+        target_repo_token: ${{ secrets.GH_PAT }}
+        upstream_sync_branch: ${{ env.UPSTREAM_BRANCH }}
+        upstream_sync_repo: ${{ env.UPSTREAM_REPO }}
+      
+    # Step 3: Display a sample message based on the sync output var 'has_new_commits'
+    - name: New commits found
+      if: steps.sync.outputs.has_new_commits == 'true'
+      run: echo "New commits were found to sync."
+    
+    - name: No new commits
+      if: steps.sync.outputs.has_new_commits == 'false'
+      run: echo echo "There were no new commits."
+      
+    - name: Show value of 'has_new_commits'
+      run: |
+        echo ${{ steps.sync.outputs.has_new_commits }}
+        echo "NEW_COMMITS=${{ steps.sync.outputs.has_new_commits }}" >> $GITHUB_OUTPUT
+        
+    # Keep upstream repository "alive": add empty commits after "time_elapsed" days to avoid inactivation of scheduled workflows
+    - name: Keep alive
+      if: (github.ref == 'refs/heads/main' && github.repository_owner == 'LoopKit')
+      uses: gautamkrishnar/keepalive-workflow@v1 # using the workflow with default settings
+      with:
+        time_elapsed: 27 # Time elapsed from the previous commit to trigger a new automated commit (in days)
+
+  # Launch build workflow if new commits are found
+  launch_build_workflow:
+    if: needs.check_latest_from_upstream.outputs.NEW_COMMITS == 'true' && (github.repository_owner != 'LoopKit')
+    needs: check_latest_from_upstream
+    name: Launch build workflow
+    uses: ./.github/workflows/build_loop.yml
+    secrets: inherit