curl --request GET \
  --url https://api.example.com/orgs/{org_id}/nodes/{node_id}/branches/diff/{source_branch}..{target_branch}

{
  "source_branch": "<string>",
  "target_branch": "<string>",
  "source_commit": "<string>",
  "target_commit": "<string>",
  "can_merge": true,
  "commits_ahead": 123,
  "commits_behind": 123,
  "merge_reason": "<string>",
  "has_conflicts": false,
  "comparison": {}
}