clang-format (#86)

* clang-format

* ignore clang-format commit; run clang-format in github actions

.github/workflows/clang-format.yml

@@ -0,0 +1,60 @@
+name: clang-format
+
+on: [push, pull_request]
+
+jobs:
+  check:
+    runs-on: ubuntu-18.04
+    env:
+      CLANG_VERSION: 10
+    steps:
+    - uses: actions/checkout@v2
+    - name: Install clang-format
+      run: |
+        sudo tee /etc/apt/sources.list.d/llvm.list >/dev/null <<EOF
+        deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-${CLANG_VERSION} main
+        deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic-${CLANG_VERSION} main
+        EOF
+        wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add
+        sudo apt-get update
+        sudo apt-get install clang-format-${CLANG_VERSION}
+    - name: Format src
+      run: find src -type f \( -name '*.cpp' -o -name '*.h' -o -name '*.ipp' \) -print0 | xargs -0 clang-format-${CLANG_VERSION} -i
+    - name: Format unittests
+      run: find unittests -type f \( -name '*.cpp' -o -name '*.h' -o -name '*.ipp' \) -print0 | xargs -0 clang-format-${CLANG_VERSION} -i
+    - name: Check for differences
+      id: assert
+      run: |
+        set -o pipefail
+        git diff --exit-code | tee "clang-format.patch"
+    - name: Upload patch
+      if: failure() && steps.assert.outcome == 'failure'
+      uses: actions/upload-artifact@v2
+      continue-on-error: true
+      with:
+        name: clang-format.patch
+        if-no-files-found: ignore
+        path: clang-format.patch
+    - name: What happened?
+      if: failure() && steps.assert.outcome == 'failure'
+      env:
+        PREAMBLE: |
+          If you are reading this, you are looking at a failed Github Actions
+          job.  That means you pushed one or more files that did not conform
+          to the formatting specified in .clang-format. That may be because
+          you neglected to run 'git clang-format' or 'clang-format' before
+          committing, or that your version of clang-format has an
+          incompatibility with the one on this
+          machine, which is:
+        SUGGESTION: |
+
+          To fix it, you can do one of two things:
+          1. Download and apply the patch generated as an artifact of this
+             job to your repo, commit, and push.
+          2. Run 'git-clang-format --extensions c,cpp,h,cxx,ipp develop'
+             in your repo, commit, and push.
+      run: |
+        echo "${PREAMBLE}"
+        clang-format-${CLANG_VERSION} --version
+        echo "${SUGGESTION}"
+        exit 1