CMake >= 3.20 required & CI enabled

.github/workflows/ci.yml

@@ -125,3 +125,36 @@ jobs:
       with:
         name: coverage-report-html
         path: build-coverage/coverage/
+
+
+  cmake-older:
+    timeout-minutes: 30
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        cmake_version: ["3.20.6"]
+
+    steps:
+
+    - uses: actions/checkout@v4
+
+    - name: prereqs
+      run: |
+        sudo apt-get update
+        sudo apt install --no-install-recommends libhdf5-dev
+
+    - uses: ./.github/workflows/composite-cmake
+
+    - name: configure
+      run: $CMAKE -Bbuild -DCMAKE_INSTALL_PREFIX:PATH=$(pwd)/build/local
+
+    - name: build
+      run: $CMAKE --build build
+
+    - name: test
+      run: $CTEST --test-dir build
+
+    - name: install package
+      run: $CMAKE --install build

.github/workflows/composite-cmake/action.yml

@@ -0,0 +1,26 @@
+runs:
+
+  using: "composite"
+
+  steps:
+  - name: environment
+    shell: bash
+    run: |
+      echo "osarch=linux-x86_64" >> $GITHUB_ENV
+      echo "archive=linux-x86_64.tar.gz" >> $GITHUB_ENV
+
+  - name: Install CMake ${{ matrix.cmake_version }}
+    shell: bash
+    run: |
+      curl -LO "https://github.com/Kitware/CMake/releases/download/v${{ matrix.cmake_version }}/cmake-${{ matrix.cmake_version }}-$archive"
+      tar -xf cmake-${{ matrix.cmake_version }}-$archive
+
+  - name: CMake path
+    shell: bash
+    run: |
+      echo "CMAKE=$GITHUB_WORKSPACE/cmake-${{ matrix.cmake_version }}-$osarch/bin/cmake" >> $GITHUB_ENV
+      echo "CTEST=$GITHUB_WORKSPACE/cmake-${{ matrix.cmake_version }}-$osarch/bin/ctest" >> $GITHUB_ENV
+
+  - name: echo CMake version
+    shell: bash
+    run: $CMAKE --version

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.19...3.30)
+cmake_minimum_required(VERSION 3.20...3.30)
 
 if(CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
   message(FATAL_ERROR "Please do out of source build like