Merge pull request #18 from jorgesolebur/feature/UseMainBranchCommitAsDefault

Use main branch latest commit if ref not specified.

Author: rupeshjSFDC

cumulusci_ado/vcs/ado/adapter.py

@@ -780,7 +780,7 @@ def get_ref(self, ref_sha: str) -> Optional[ADORef]:
             refs: list[GitRef] = self.git_client.get_refs(
                 self.id,
                 self.project_id,
-                filter=ref_sha,
+                filter=(ref_sha or f"heads/{self.default_branch}"),
                 include_statuses=True,
                 latest_statuses_only=True,
                 peel_tags=True,