workflows: Skip jobs instead of workflows

In its initial version, commit 3ceb742 (".github: Skip unnecessary docs
test") skipped the job instead of the whole workflow, based on changed
code paths. After discussion on the pull request [1], we figured we
could save some seconds by skipping the whole workflow instead of the
job. Skipping the job requires adding a new job to check the code paths.

However, if we skip the whole workflow, the job status is never reported
on GitHub. Since the documentation job is required to merge, that means
maintainer's little helper will never mark the pull request as ready to
merge.

Thus, this commit reverts back to skipping the jobs instead of the whole
workflows. To that end, we use paths-filter GitHub Action instead of the
direct GitHub integration (since the GitHub path filters can only skip
the whole workflow).

1 - #16157 (comment)
Signed-off-by: Paul Chaignon <paul@cilium.io>

.github/workflows/documentation.yaml

@@ -2,33 +2,41 @@ name: Documentation Updates
 
 # Any change in triggers needs to be reflected in the concurrency group.
 on:
-  pull_request:
-    paths:
-      - 'Documentation/**'
-      - 'bugtool/cmd/**'
-      - 'cilium/cmd/**'
-      - 'cilium-health/cmd/**'
-      - 'daemon/cmd/**'
-      - 'hubble-relay/cmd/**'
-      - 'operator/cmd/**'
+  pull_request: {}
   push:
     branches:
       - master
-    paths:
-      - 'Documentation/**'
-      - 'bugtool/cmd/**'
-      - 'cilium/cmd/**'
-      - 'cilium-health/cmd/**'
-      - 'daemon/cmd/**'
-      - 'hubble-relay/cmd/**'
-      - 'operator/cmd/**'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.event.after }}
   cancel-in-progress: true
 
 jobs:
+  check_changes:
+    name: Deduce required tests from code changes
+    runs-on: ubuntu-18.04
+    outputs:
+      docs-tree: ${{ steps.docs-tree.outputs.src }}
+    steps:
+      - name: Check code changes
+        uses: dorny/paths-filter@78ab00f87740f82aec8ed8826eb4c3c851044126
+        id: docs-tree
+        with:
+          filters: |
+            src:
+              - 'Documentation/**'
+              - 'bugtool/cmd/**'
+              - 'cilium/cmd/**'
+              - 'cilium-health/cmd/**'
+              - 'daemon/cmd/**'
+              - 'hubble-relay/cmd/**'
+              - 'operator/cmd/**'
+
+  # Runs only if code under Documentation or */cmd/ is changed as the docs
+  # should be unaffected otherwise.
   build-html:
+    needs: check_changes
+    if: ${{ needs.check_changes.outputs.docs-tree == 'true' }}
     name: Validate & Build HTML
     runs-on: ubuntu-18.04
     steps:

.github/workflows/lint-codeql.yaml

@@ -1,22 +1,31 @@
 name: codeql
 
 on:
-  push:
-    paths:
-      - '*.go'
-      - 'go.mod'
-      - 'go.sum'
-  pull_request:
-    paths:
-      - '*.go'
-      - 'go.mod'
-      - 'go.sum'
+  push: {}
+  pull_request: {}
   schedule:
     - cron: "45 6 * * 3"
 
 jobs:
+  check_changes:
+    name: Deduce required tests from code changes
+    runs-on: ubuntu-18.04
+    outputs:
+      go-changes: ${{ steps.go-changes.outputs.src }}
+    steps:
+      - name: Check code changes
+        uses: dorny/paths-filter@78ab00f87740f82aec8ed8826eb4c3c851044126
+        id: go-changes
+        with:
+          filters: |
+            src:
+              - '*.go'
+              - 'go.mod'
+              - 'go.sum'
+
   analyze:
-    if: github.repository == 'cilium/cilium'
+    needs: check_changes
+    if: github.repository == 'cilium/cilium' && needs.check_changes.outputs.go-changes == 'true'
     runs-on: ubuntu-18.04
     steps:
     - name: Checkout repo

.github/workflows/tests-smoke-ipv6.yaml

@@ -2,16 +2,10 @@ name: Smoke Test with IPv6
 
 # Any change in triggers needs to be reflected in the concurrency group.
 on:
-  pull_request:
-    paths-ignore:
-      - 'Documentation/**'
-      - 'test/**'
+  pull_request: {}
   push:
     branches:
       - master
-    paths-ignore:
-      - 'Documentation/**'
-      - 'test/**'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.event.after }}
@@ -26,8 +20,23 @@ env:
   LOG_TIME: 30m
 
 jobs:
+  check_changes:
+    name: Deduce required tests from code changes
+    runs-on: ubuntu-18.04
+    outputs:
+      tested: ${{ steps.tested-tree.outputs.src }}
+    steps:
+      - name: Check code changes
+        uses: dorny/paths-filter@78ab00f87740f82aec8ed8826eb4c3c851044126
+        id: tested-tree
+        with:
+          filters: |
+            src:
+              - '!(test|Documentation)/**'
+
   conformance-test-ipv6:
-    if: ${{ github.repository == 'cilium/cilium' }}
+    needs: check_changes
+    if: ${{ github.repository == 'cilium/cilium' && needs.check_changes.outputs.tested == 'true' }}
     runs-on: ubuntu-latest
     steps:
       - name: Checkout

.github/workflows/tests-smoke.yaml

@@ -2,16 +2,10 @@ name: Smoke test
 
 # Any change in triggers needs to be reflected in the concurrency group.
 on:
-  pull_request:
-    paths-ignore:
-      - 'Documentation/**'
-      - 'test/**'
+  pull_request: {}
   push:
     branches:
       - master
-    paths-ignore:
-      - 'Documentation/**'
-      - 'test/**'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.event.after }}
@@ -25,6 +19,20 @@ env:
   LOG_TIME: 30m
 
 jobs:
+  check_changes:
+    name: Deduce required tests from code changes
+    runs-on: ubuntu-18.04
+    outputs:
+      tested: ${{ steps.tested-tree.outputs.src }}
+    steps:
+      - name: Check code changes
+        uses: dorny/paths-filter@78ab00f87740f82aec8ed8826eb4c3c851044126
+        id: tested-tree
+        with:
+          filters: |
+            src:
+              - '!(test|Documentation)/**'
+
   preflight-clusterrole:
     runs-on: ubuntu-latest
     steps:
@@ -69,7 +77,8 @@ jobs:
           git diff --exit-code || (echo "please run 'make -C install/kubernetes docs' and submit your changes"; exit 1)
 
   conformance-test:
-    if: ${{ github.repository == 'cilium/cilium' }}
+    needs: check_changes
+    if: ${{ github.repository == 'cilium/cilium' && needs.check_changes.outputs.tested == 'true' }}
     runs-on: ubuntu-latest
     steps:
       - name: Checkout