Merge pull request #1537 from opensafely/iaindillingham/fix-push-to-g…

…ithub

Fix "Push to GitHub" section

docs/getting-started/how-to/add-github-codespaces-to-your-project/index.md

@@ -95,7 +95,7 @@ git commit --message="Add GitHub Codespaces"
 Push to GitHub:
 
 ```sh
-git push
+git push --set-upstream
 ```
 
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