I cannot fathom why people are still actively supporting GitHub.
Even if you ignore the ethical reasons, which if you are an open source developer really should suffice, GitLab is better and more customizable in every way.
Supporting it benefits yourself and all of the FOSS community.
Git repositories do have a full copy of the codebase (unless using some large-file management, same issue with largefiles extension for hg).
But gitlab/github are more than just git repositories -- issue tracking, discussions, wiki, etc. One version control which includes most of this as part of the repository is fossil, http://fossil-scm.org
I cannot fathom why people are still actively supporting GitHub.
Even if you ignore the ethical reasons, which if you are an open source developer really should suffice, GitLab is better and more customizable in every way.
Supporting it benefits yourself and all of the FOSS community.