All new Git repositories on GitHub will be named "main" instead of "master" starting October 1, 2020.

Both Conservancy and the Git project are aware that the initial branch name, ‘master’, is
offensive to some people and we empathize with those hurt by the use of that term.Existing versions of Git are capable of working with any branch name; there's nothing special about ‘master’ except that it has historically been the name used for the first branch when creating a new repository from scratch (with the git init command). Thus many projects use it to represent the primary line of development. We support and encourage projects to switch to branch names that are meaningful and inclusive, and we'll be adding features to Git to make it even easier to use a different default for new projects.