SDK fixes for github actions. (#36)

`get_past_n_ancestors` would crash in python if `git merge-base` was
failing. Also made the TS and PY implementations more aligned.

js/src/gitutil.ts

@@ -110,6 +110,9 @@ export async function getPastNAncestors(
       `${e}`
     );
   }
+  if (!ancestor) {
+    return [];
+  }
   const commits = await git.log({ from: ancestor, to: "HEAD" });
   return commits.all.map((c) => c.hash);
 }

py/src/braintrust/gitutil.py

@@ -82,7 +82,7 @@ def _get_base_branch_ancestor(remote=None):
     try:
         return subprocess.check_output(["git", "merge-base", head, f"{remote_name}/{base_branch}"]).decode().strip()
     except subprocess.CalledProcessError as e:
-        _logger.warning(f"Could not find a common ancestor with {remote_name}/{base_branch}", e)
+        # _logger.warning(f"Could not find a common ancestor with {remote_name}/{base_branch}")
         return None
 
 
@@ -92,7 +92,10 @@ def get_past_n_ancestors(n=10, remote=None):
         if repo is None:
             return
 
-        ancestor = repo.commit(_get_base_branch_ancestor())
+        ancestor_output = _get_base_branch_ancestor()
+        if ancestor_output is None:
+            return
+        ancestor = repo.commit(ancestor_output)
         for _ in range(n):
             yield ancestor.hexsha
             if ancestor.parents: