Only require ref to exist when using tag/branch

Changes to the GitHub GraphQL API mean that resolving
references with `HEAD` no longer work.

However, we don't need to actually do this when
providing a commit SHA as a base,
so we can move the error check to only when
we need this information when committing to the same
branch as the base.

Author: s0

.changeset/shaggy-eels-promise.md

@@ -0,0 +1,5 @@
+---
+"@s0/ghcommit": patch
+---
+
+Address issue with Ref HEAD not found

src/core.ts

@@ -79,10 +79,6 @@ export const commitFilesFromBase64 = async ({
     throw new Error(`Repository ${repositoryNameWithOwner} not found`);
   }
 
-  if (!info.baseRef) {
-    throw new Error(`Ref ${baseRef} not found`);
-  }
-
   const repositoryId = info.id;
   /**
    * The commit oid to base the new commit on.
@@ -97,6 +93,10 @@ export const commitFilesFromBase64 = async ({
   if ("branch" in base && base.branch === branch) {
     log?.debug(`Committing to the same branch as base: ${branch} (${baseOid})`);
     // Get existing branch refId
+
+    if (!info.baseRef) {
+      throw new Error(`Ref ${baseRef} not found`);
+    }
     refId = info.baseRef.id;
   } else {
     // Determine if the branch needs to be created or not