Edit:
Since theres been some confusion with dates
In 2016 github made site side searching login only and hid the search bar if you werent logged in. This didnt include searching within a repository so that could still be done, just not all repositories
This year was the change being referred to in this link which made repository level searching require logging in
Blog post: https://github.blog/changelog/2023-06-07-code-search-now-requires-login/
deleted by creator
As long as I can remember
If you used the top search bar, there was always this tab selection.
The looks changed a few month ago, but the featureset was visually the same.