Add GitHub Actions (#1193)

.github/workflows/test.yml

+name: "Run tests"
+
+on:
+  - push
+  - pull_request
+
+env:
+  FORMAT_FILE: README.md
+
+jobs:
+  test:
+    name: 'Validate README.md'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Validate Markdown format
+        run: build/validate_format.py ${FORMAT_FILE}
+
+      - name: Validate pull request changes
+        run: build/github-pull.sh ${{ github.repository }} ${{ github.event.pull_request.number }} ${FORMAT_FILE}
+        if: github.event_name == 'pull_request'

build/github-pull.sh

+#!/usr/bin/env bash
+
+set -e
+
+# Argument validation
+if [ $# -ne 3 ]; then
+    echo "Usage: $0 <github-repo> <pull-number> <format-file>"
+    exit 1
+fi
+
+# Assign variables
+GITHUB_REPOSITORY="$1"
+GITHUB_PULL_REQUEST="$2"
+FORMAT_FILE="$3"
+
+# Move to root of project
+cd "$GITHUB_WORKSPACE"
+
+# Determine files
+FORMAT_FILE="$( realpath "${FORMAT_FILE}" )"
+
+# Skip if build number could not be determined
+if [ -z "$GITHUB_REPOSITORY" -o -z "$GITHUB_PULL_REQUEST" ]; then
+    echo "No pull request and/or repository is provided"
+    exit 1
+fi
+
+# Pull changes on PR
+echo "running on Pull Request #$GITHUB_PULL_REQUEST"
+
+# Trick the URL validator python script into not seeing this as a URL
+DUMMY_SCHEME="https"
+DIFF_URL="$DUMMY_SCHEME://patch-diff.githubusercontent.com/raw/$GITHUB_REPOSITORY/pull/$GITHUB_PULL_REQUEST.diff"
+curl -L -o diff.txt "$DIFF_URL"
+
+# Construct diff
+echo "------- BEGIN DIFF -------"
+cat diff.txt
+echo "-------- END DIFF --------"
+cat diff.txt | egrep "\+" > additions.txt
+
+echo "------ BEGIN ADDITIONS -----"
+cat additions.txt
+echo "------- END ADDITIONS ------"
+LINK_FILE=additions.txt
+
+# Validate links
+echo "Running link validation..."
+./build/validate_links.py "$LINK_FILE"
+
+# Vebosity
+if [[ $? != 0 ]]; then
+    echo "link validation failed!"
+    exit 1
+else
+    echo "link validation passed!"
+fi