fix: dynamic determinal of commit SHA

Author: rdhar

action.yml

@@ -23,7 +23,7 @@ runs:
         # Get PR number using GitHub API for different event triggers.
         if [[ "$GITHUB_EVENT_NAME" == "push" ]]; then
           # List PRs associated with the commit, then get the PR number from the head ref or the latest PR.
-          associated_prs=$(gh api /repos/${{ github.repository }}/commits/${GITHUB_SHA}/pulls --header "$GH_API" --method GET --field per_page=100)
+          associated_prs=$(gh api /repos/${{ github.repository }}/commits/${{ github.event.pull_request.head.sha || github.sha }}/pulls --header "$GH_API" --method GET --field per_page=100)
           number=$(echo "$associated_prs" | jq --raw-output '(.[] | select(.head.ref == env.GITHUB_REF_NAME) | .number) // .[0].number // 0')
         elif [[ "$GITHUB_EVENT_NAME" == "merge_group" ]]; then
           # Get the PR number by parsing the ref name.