From c2a32d4269715e71c8872d571c9306070081a821 Mon Sep 17 00:00:00 2001
From: Quentin Monnet <qmo@qmon.net>
Date: Mon, 11 Nov 2024 15:53:44 +0000
Subject: [PATCH] ci: Skip dev.yml, sterile.yml if there are no code changes

Skip dev.yml and sterile.yml workflows if there are no relevant code
change. This means we skip the main jobs if the only files changed in
the PR are README.md, LICENSE, .gitignore, anything under design-docs,
or anything under .github and apart from the definition of the workflow
itself.

Signed-off-by: Quentin Monnet <qmo@qmon.net>
---
 .github/workflows/dev.yml     | 31 +++++++++++++++++++++++++++++++
 .github/workflows/sterile.yml | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/.github/workflows/dev.yml b/.github/workflows/dev.yml
index 09758223..3021aedc 100644
--- a/.github/workflows/dev.yml
+++ b/.github/workflows/dev.yml
@@ -29,7 +29,38 @@ permissions:
   id-token: "write"
 
 jobs:
+  check_changes:
+    name: "Deduce required tests from code changes"
+    runs-on: "ubuntu-latest"
+    outputs:
+      devfiles: "${{ steps.changes.outputs.devfiles }}"
+    steps:
+      - name: "Checkout"
+        if: "${{ !github.event.pull_request }}"
+        uses: "actions/checkout@v4"
+        with:
+          persist-credentials: "false"
+          fetch-depth: "0"
+      - name: "Check code changes"
+        uses: "dorny/paths-filter@v3"
+        id: "changes"
+        with:
+          # For "push" events, compare against the "ref" base branch.
+          # For "pull_request" events, this is ignored and will compare against
+          # the pull request base branch.
+          base: "${{ github.ref }}"
+          filters: |
+            devfiles:
+              - '**/**'
+              - '!README.md'
+              - '!LICENSE'
+              - '!design-docs/**'
+              - '!.gitignore'
+              - '!.github/**'
+              - '.github/workflows/dev.yml'
+
   build:
+    if: "${{ needs.check_changes.outputs.devfiles == 'true' }}"
     strategy:
       fail-fast: false
       matrix:
diff --git a/.github/workflows/sterile.yml b/.github/workflows/sterile.yml
index b0dd1b12..22a82df5 100644
--- a/.github/workflows/sterile.yml
+++ b/.github/workflows/sterile.yml
@@ -18,7 +18,38 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  check_changes:
+    name: "Deduce required tests from code changes"
+    runs-on: "ubuntu-latest"
+    outputs:
+      devfiles: "${{ steps.changes.outputs.devfiles }}"
+    steps:
+      - name: "Checkout"
+        if: "${{ !github.event.pull_request }}"
+        uses: "actions/checkout@v4"
+        with:
+          persist-credentials: "false"
+          fetch-depth: "0"
+      - name: "Check code changes"
+        uses: "dorny/paths-filter@v3"
+        id: "changes"
+        with:
+          # For "push" events, compare against the "ref" base branch.
+          # For "pull_request" events, this is ignored and will compare against
+          # the pull request base branch.
+          base: "${{ github.ref }}"
+          filters: |
+            devfiles:
+              - '**/**'
+              - '!README.md'
+              - '!LICENSE'
+              - '!design-docs/**'
+              - '!.gitignore'
+              - '!.github/**'
+              - '.github/workflows/sterile.yml'
+
   test:
+    if: "${{ needs.check_changes.outputs.devfiles == 'true' }}"
     permissions:
       contents: "read"
       packages: "read"
@@ -137,6 +168,7 @@ jobs:
           limit-access-to-actor: true
 
   push:
+    if: "${{ needs.check_changes.outputs.devfiles == 'true' }}"
     permissions:
       contents: "read"
       packages: "write"