GitHub search is notoriously poor, though—it can only match whole words (e.g. the query "FooBar" does not match the text "FooBarBaz"), and it doesn't support regexes.

In addition to the flaws mentioned by the other commenters (whole word only, no regexes), Github will only search the master branch of a repo, which makes it useless for my two most common tasks "where did this code used to be used" and "does this unmerged PR manage to remove all of the references to this code in its refactor (incl. in comments/etc)"

EDIT: Unfortunately, it seems like search doesn't work at all on this site, which is a shame. (at least, when I tried to do it on https://github1s.com/rails/rails it failed)

It does have search, but I'd be willing to wager that the normal workflow when using that is "try searching for something, look at the results page, swear, clone, ..."

How does that work? I've never been able to find this option. Also, this tool's search is broken. It searches only the currently open file.

And as long as you’re not trying to do a case-sensitive search.