A data model for Git (and other docs updates)

The author decided to improve Git's documentation after previously writing blog posts and zines. They collaborated with Marie to create a "data model" document explaining Git's core concepts like objects, references, and the index. The author updated introductions to several Git man pages like `git push` and `git pull`. They realized that a more evidence-based approach was needed to identify documentation problems. The author asked for test readers on Mastodon to provide feedback on the existing documentation. Test readers identified confusing terminology, unclear sentences, and inconsistencies in the documentation. This feedback helped the author improve the man pages for `git add`, `git checkout`, `git push`, and `git pull`. The author found the changes for `git push` and `git pull` most interesting, including definitions for "upstream branch" and "push refspec". Contributing to Git involved learning its development process, including using the Discord server and GitGitGadget. They found the Git community welcoming and received help from many contributors. The author also created a custom Git list viewer to navigate mailing list archives.