How did I get the git commits to show up in autocomplete?

Git tab completion on my mac: Git tab completion on my Ubuntu server: On my mac and my Ubuntu server I get very different output from tab completion despite having the same version of zsh, same version of git, the same version of oh-my-zsh, and the same .zshrc file. I wanted to know what is giving me the ability to see commits on my mac using tab completion so that I can set it up on my ubuntu server.