test: use variable to specify target branch

Author: SergeantBiggs

.ci/ct.yaml

@@ -1,5 +1,4 @@
 ---
-remote: origin/master
 chart-dirs:
   - charts
 chart-repos:

.github/workflows/chart-testing.yaml

@@ -40,14 +40,14 @@ jobs:
       - name: Run chart-testing (list-changed)
         id: list-changed
         run: |
-          changed=$(ct list-changed --config .ci/ct.yaml)
+          changed=$(ct list-changed --target-branch ${{ github.event.repository.default_branch }} --config .ci/ct.yaml)
           if [[ -n "$changed" ]]; then
             echo "::set-output name=changed::true"
           fi
 
       - name: Run chart-testing (lint)
         id: lint
-        run: ct lint --config .ci/ct.yaml
+        run: ct lint --target-branch ${{ github.event.repository.default_branch }} --config .ci/ct.yaml
 
       - name: Create kind cluster
         uses: helm/kind-action@v1.12.0
@@ -67,6 +67,6 @@ jobs:
         if: steps.list-changed.outputs.changed == 'true'
 
       - name: Run chart-testing (install)
-        run: ct install --config .ci/ct.yaml
+        run: ct install --target-branch ${{ github.event.repository.default_branch }} --config .ci/ct.yaml
         # Only install if there are chart changes to test.
         if: steps.list-changed.outputs.changed == 'true'