perf: avoid extra PR fetch for merge-only update-pull-request

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/340b546b-743d-45b6-ac7e-8ec5735124d3

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Author: Copilot

actions/setup/js/update_pull_request.cjs

@@ -89,12 +89,10 @@ async function executePRUpdate(github, context, prNumber, updateData) {
   }
 
   if (Object.keys(apiData).length === 0) {
-    const { data: pr } = await github.rest.pulls.get({
-      owner: context.repo.owner,
-      repo: context.repo.repo,
-      pull_number: prNumber,
-    });
-    return pr;
+    return {
+      number: prNumber,
+      html_url: `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/pull/${prNumber}`,
+    };
   }
 
   const { data: pr } = await github.rest.pulls.update({

actions/setup/js/update_pull_request.test.cjs

@@ -802,6 +802,7 @@ describe("update_pull_request.cjs - merge_base behavior", () => {
       repo: "testrepo",
       pull_number: 100,
     });
+    expect(mockGithub.rest.pulls.get).not.toHaveBeenCalled();
     expect(mockGithub.rest.pulls.update).not.toHaveBeenCalled();
   });