Rewrite the ref to correctly point to refs/remotes

Fixes the rev-parse issues caused by #428

Author: Simon Engledew

lib/actions-util.js

@@ -40,7 +40,7 @@ test("getRef() returns merge PR ref if GITHUB_REF still checked out but sha has
   const sha = "a".repeat(40);
 
   const callback = sinon.stub(actionsutil, "getCommitOid");
-  callback.withArgs("refs/pull/1/merge").resolves(sha);
+  callback.withArgs("refs/remotes/pull/1/merge").resolves(sha);
   callback.withArgs("HEAD").resolves(sha);
 
   const actualRef = await actionsutil.getRef();

lib/actions-util.js.map

@@ -443,7 +443,10 @@ export async function getRef(): Promise<string> {
   // using GITHUB_REF. There is a subtle race condition where
   // git rev-parse GITHUB_REF != GITHUB_SHA, so we must check
   // git git-parse GITHUB_REF == git rev-parse HEAD instead.
-  const hasChangedRef = sha !== head && (await getCommitOid(ref)) !== head;
+  const hasChangedRef =
+    sha !== head &&
+    (await getCommitOid(ref.replace(/^refs\/pull\//, "refs/remotes/pull/"))) !==
+      head;
 
   if (hasChangedRef) {
     const newRef = ref.replace(pull_ref_regex, "refs/pull/$1/head");