Migrate CI to Github Actions (#2466)

* Migrate CI to Github Actions

Replaces current Travis setup.

Benefits include:
- Faster
- Multiple families can now be included in a single PR
- PRs can come from forked repos

Fixes #2463

* Restore travis file temporarily

.ci/run_gh.sh

@@ -0,0 +1,32 @@
+# Only run gftools qa on prs which have modified files in directories which
+# contain font binaries.
+
+# Find directories which contain files that have been altered or added. Also
+# Skip /static directories.
+CHANGED_DIRS=$(git diff origin/master --dirstat=files --diff-filter d | sed "s/[0-9. ].*%//g" | grep -v "static")
+OUT=out
+
+
+for dir in $CHANGED_DIRS
+do
+    font_count=$(ls -1 $dir*.ttf 2>/dev/null | wc -l)
+    if [ $font_count != 0 ]
+    then
+	echo "Checking $dir"
+	mkdir -p $OUT
+	# If pr contains modified fonts, check with Fontbakery, Diffenator and DiffBrowsers.
+	# If pr doesn't contain modified fonts, just check with Fontbakery.
+	modified_fonts=$(git diff --name-only origin/master HEAD $dir*.ttf)
+	if [ -n "$modified_fonts" ]
+	then
+	    echo "Fonts have been modified. Checking fonts with all tools"
+	    gftools qa -f $dir*.ttf -gfb -a -o $OUT/$(basename $dir)_qa
+	else
+	    echo "Fonts have not been modified. Checking fonts with Fontbakery only"
+	    gftools qa -f $dir*.ttf --fontbakery -o $OUT/$(basename $dir)_qa
+	fi
+    else
+	echo "Skipping $dir. Directory does not contain fonts"
+    fi
+done
+

.github/workflows/test.yaml

@@ -0,0 +1,42 @@
+name: Google Fonts QA
+on: [pull_request]
+
+jobs:
+
+  build:
+    name: Build Google Fonts
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Setup python
+        uses: actions/setup-python@v1
+        with:
+          # TODO use build matrix?
+          python-version: 3.8
+
+      - name: Install dependencies
+        run: |
+          sudo apt install libharfbuzz-dev libharfbuzz-bin libfreetype6-dev libglib2.0-dev libcairo2-dev
+          python -m pip install --upgrade pip
+          pip install gftools[qa]
+      - name: Check fonts
+        env:
+          GF_API_KEY: ${{ secrets.GF_API_KEY }}
+          BSTACK_ACCESS_KEY: ${{ secrets.BSTACK_ACCESS_KEY }}
+          BSTACK_USERNAME: ${{ secrets.BSTACK_USERNAME }}
+        run: |
+          sh .ci/run_gh.sh
+
+      - name: Check file existence
+        id: check_files
+        uses: andstor/file-existence-action@v1
+        with:
+          files: "out"
+
+      - name: Upload check results
+        if: steps.check_files.outputs.files_exists == 'true'
+        uses: actions/upload-artifact@v1
+        with:
+          name: qa
+          path: out/
+