message: Comment why ubuntu 16.04, use 18.04 otherwise
diff: @@ -21,7 +21,7 @@ on:
  jobs:
  copyright-check:
  - runs-on: ubuntu-16.04
  + runs-on: ubuntu-18.04 # needed for astyle 2.05.1
  steps:
  - name: checkout mfem
  @@ -42,7 +42,7 @@ jobs:
  fi
  code-style:
  - runs-on: ubuntu-16.04
  + runs-on: ubuntu-16.04 # needed for astyle 2.05.1
  steps:
  - name: checkout mfem
  @@ -58,7 +58,7 @@ jobs:
  ./runtest code-style
  documentation:
  - runs-on: ubuntu-16.04
  + runs-on: ubuntu-18.04
  steps:
  - name: checkout mfem
  @@ -75,7 +75,7 @@ jobs:
  branch-history:
  if: github.ref != 'refs/heads/next'
  - runs-on: ubuntu-16.04
  + runs-on: ubuntu-18.04
  steps:
  - name: checkout mfem
  