ci: Improve CI trigger and concurrency

Outdated CI jobs will now be cancelled and a workflow is only run if
relevant files were changed.
Additionally, the CI only runs on pull requests to the main branch.

.github/workflows/cmake-lint.yml

@@ -1,9 +1,14 @@
 name: "CMake Lint"
 
 on:
-  push:
-    paths-ignore:
-      - 'README.md'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**/CMakeLists.txt'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   lint:

.github/workflows/cpp-build.yml

@@ -1,9 +1,18 @@
 name: "C++ Build"
 
 on:
-  push:
-    paths-ignore:
-      - 'README.md'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - 'src/**'
+      - 'include/**'
+      - 'test/**'
+      - 'examples/**'
+      - 'CMakeLists.txt'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   build:

.github/workflows/cpp-lint.yml

@@ -1,9 +1,19 @@
 name: "C++ Lint"
 
 on:
-  push:
-    paths-ignore:
-      - 'README.md'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - 'src/**/*.cpp'
+      - 'include/**/*.h'
+      - 'test/**/*.cpp'
+      - 'test/**/*.h'
+      - 'examples/**/*.cpp'
+      - 'examples/**/*.h'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   lint:

.github/workflows/cpp-unittest.yml

@@ -1,9 +1,18 @@
 name: "C++ Unittests"
 
 on:
-  push:
-    paths-ignore:
-      - 'README.md'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - 'src/**'
+      - 'include/**'
+      - 'test/**'
+      - 'CMakeLists.txt'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 
 jobs:
   unittest:

.github/workflows/format.yml

@@ -1,9 +1,16 @@
 name: "C++/CMake Format"
 
 on:
-  push:
-    paths-ignore:
-      - 'README.md'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**/*.cpp'
+      - '**/*.h'
+      - '**/CMakeLists.txt'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   format: