xpath expression is correct. Base on API, ```sha``` should be a node, not attr. 
```
public JsonObject json() throws IOException {
        return new JsonNode(
            this.storage.xml().nodes(
                String.format(
                    "/github/repos/repo[@coords='%s']/commits/commit[sha='%s']",
                        this.repo().coordinates(), this.hash
                )
            ).get(0)
        ).json();
    }

```