CI: Separate C++ linting (#4400)

* separate cpp lint

* made executable

.ci/lint_cpp.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+
+# fetch master branch
+git fetch origin master
+
+# unshallow if needed
+echo "Finding merge base"
+if ! git merge-base origin/master HEAD; then
+  echo "Could not find merge base, unshallowing repo"
+  git fetch --unshallow
+fi
+
+# Check formatting using clangify
+echo "Checking your code using clang-format..."
+
+diff="$(./clangify.sh --diff --cf-version --branch origin/master)"
+err=$?
+
+case $err in
+  1)
+    cat <<EOM
+
+***********************************************************
+***                                                     ***
+***   Your code does not comply with our style guide.   ***
+***                                                     ***
+***  Please correct it or run the "clangify.sh" script. ***
+***  Then commit and push those changes to this branch. ***
+***   Check our CONTRIBUTING.md file for more details.  ***
+***                                                     ***
+***                    Thank you ❤️                      ***
+***                                                     ***
+***********************************************************
+
+Used clang-format version:
+${diff%%
+*}
+
+The following changes should be made:
+${diff#*
+}
+
+Exiting...
+EOM
+      exit 2
+      ;;
+
+    0)
+      cat <<EOM
+
+***********************************************************
+***                                                     ***
+***       Your code complies with our style guide!      ***
+***                                                     ***
+***                      Awesome 👍                     ***
+***                                                     ***
+***********************************************************
+
+Exiting...
+EOM
+      exit 0
+      ;;
+
+    *)
+      echo ""
+      echo "Something went wrong in our formatting checks: clangify returned $err" >&2
+      echo ""
+      ;;
+  esac