Get a reference

Returns a single reference from your Git database. The `:ref` in the URL must be formatted as `heads/<branch name>` for branches and `tags/<tag name>` for tags. If the `:ref` doesn't match an existing ref, a `404` is returned. **Note:** You need to explicitly [request a pull request](https://docs.github.com/[email protected]/rest/reference/pulls#get-a-pull-request) to trigger a test merge commit, which checks the mergeability of pull requests. For more information, see "[Checking mergeability of pull requests](https://docs.github.com/[email protected]/rest/guides/getting-started-with-the-git-database-api#checking-mergeability-of-pull-requests)".