Support onlyDiff=true

Author: erikn69

Diff for: entrypoint.sh

@@ -31,6 +31,15 @@ if [[ "${INPUT_PRESET}" ]]; then
   pint_command+=" --preset ${INPUT_PRESET}"
 fi
 
+if [[ "${INPUT_ONLYDIFF}" == true ]]; then
+  if [[ -n "${GITHUB_TOKEN}" ]]; then
+    INPUT_ONLYDIFF=$(curl -s -H "Authorization: token $GITHUB_TOKEN" \
+      "https://api.github.com/repos/${GITHUB_REPOSITORY}" | jq -r .default_branch)
+  else
+    INPUT_ONLYDIFF=$(git symbolic-ref refs/remotes/origin/HEAD | sed 's@^refs/remotes/origin/@@')
+  fi
+fi
+
 if [[ "${INPUT_ONLYDIFF}" ]]; then
   pint_command+=" --diff=${INPUT_ONLYDIFF}"
   INPUT_ONLYDIRTY=false