Handle hidden refs (#1774)

Co-authored-by: Chris Gavin <chris@chrisgavin.me>

src/ref-helper.ts

@@ -42,9 +42,13 @@ export async function getCheckoutInfo(
     result.ref = `refs/remotes/pull/${branch}`
   }
   // refs/tags/
-  else if (upperRef.startsWith('REFS/')) {
+  else if (upperRef.startsWith('REFS/TAGS/')) {
     result.ref = ref
   }
+  // refs/
+  else if (upperRef.startsWith('REFS/') && commit) {
+    result.ref = commit
+  }
   // Unqualified ref, check for a matching branch or tag
   else {
     if (await git.branchExists(true, `origin/${ref}`)) {