fix graphql usage

Author: Andarist

src/core.ts

@@ -197,9 +197,7 @@ export const commitFilesFromBase64 = async ({
       fileChanges,
     });
 
-    const tempRefTarget = tempCommit.createCommitOnBranch?.ref?.target;
-    const tempHeadOid =
-      tempRefTarget?.__typename === "Commit" ? tempRefTarget.oid : null;
+    const tempHeadOid = tempCommit.createCommitOnBranch?.commit?.oid;
 
     if (!tempHeadOid) {
       throw new Error(

src/github/graphql/queries.ts

@@ -78,13 +78,11 @@ const DELETE_REF = /* GraphQL */ `
 const CREATE_COMMIT_ON_BRANCH = /* GraphQL */ `
   mutation createCommitOnBranch($input: CreateCommitOnBranchInput!) {
     createCommitOnBranch(input: $input) {
+      commit {
+        oid
+      }
       ref {
         id
-        target {
-          ... on Commit {
-            oid
-          }
-        }
       }
     }
   }