check if index.yaml already exists

Author: Knappek

.travis.yml

@@ -67,7 +67,7 @@ jobs:
         - git config remote.origin.fetch "+refs/heads/*:refs/remotes/origin/*"
         - git fetch origin
         - git checkout gh-pages
-        - git checkout $(git rev-list -n1 HEAD -- index.yaml)~1 -- index.yaml > /dev/null 2>&1 | true
+        - test -e index.yaml || git checkout $(git rev-list -n1 HEAD -- index.yaml)~1 -- index.yaml
         - git add index.yaml
         - git diff-index --quiet HEAD || git commit -m "Auto-restore Helm chart repo index after Docusaurus publish"
         - git push