CI: Make auto-triage more robust (#53)

- Add a global "triage" workflow instead of only changelogs.
- Add a check for updated unit tests.

Author: ZeroIntensity

.github/workflows/changelog.yml

@@ -0,0 +1,67 @@
+name: Triage
+on:
+  pull_request:
+    types:
+      - "opened"
+      - "reopened"
+      - "synchronize"
+      - "labeled"
+      - "unlabeled"
+
+jobs:
+  changelog_check:
+    runs-on: ubuntu-latest
+    name: Check for changelog updates
+    steps:
+      - name: "Check if the source directory was changed"
+        uses: dorny/paths-filter@v3
+        id: changes
+        with:
+          filters: |
+            src:
+              - 'src/**'
+
+      - name: "Check for changelog updates"
+        if: steps.changes.outputs.src == 'true'
+        uses: brettcannon/check-for-changed-files@v1
+        with:
+          file-pattern: |
+            CHANGELOG.md
+          skip-label: "skip changelog"
+          failure-message: "Missing a CHANGELOG.md update; please add one or apply the ${skip-label} label to the pull request"
+
+  tests_check:
+    runs-on: ubuntu-latest
+    name: Check for updated tests
+    steps:
+      - name: "Check if the source directory was changed"
+        uses: dorny/paths-filter@v3
+        id: changes
+        with:
+          filters: |
+            src:
+              - 'src/**'
+
+      - name: "Check for test updates"
+        if: steps.changes.outputs.src == 'true'
+        uses: brettcannon/check-for-changed-files@v1
+        with:
+          file-pattern: |
+            tests/*
+          skip-label: "skip tests"
+          failure-message: "Missing unit tests; please add some or apply the ${skip-label} label to the pull request"
+
+  all_green:
+    runs-on: ubuntu-latest
+    name: PR has no missing information
+    if: always()
+
+    needs:
+      - changelog_check
+      - tests_check
+
+    steps:
+      - name: Check whether jobs passed
+        uses: re-actors/alls-green@release/v1
+        with:
+          jobs: ${{ toJSON(needs) }}