If fugitive.vim is the Git, rhubarb.vim is the Hub. Here's the full list of features:

• Enables :GBrowse from fugitive.vim to open GitHub URLs.

• In commit messages, GitHub issues, issue URLs, and collaborators can be omni-completed (<C-X><C-O>, see :help compl-omni). This makes inserting those Closes #123 remarks slightly easier than copying and pasting from the browser.

If you don't have a preferred installation method, I recommend installing pathogen.vim, and then simply copy and paste:

cd ~/.vim/bundle
git clone https://github.com/tpope/vim-rhubarb.git
vim -u NONE -c "helptags vim-rhubarb/doc" -c q

You'll also need fugitive.vim.

Curl (included with macOS) is required for features that use the GitHub API (i.e., :GBrowse doesn't need it). Generate a personal access token with repo permissions and add it to your .netrc:

echo 'machine api.github.com login <user> password <token>' >> ~/.netrc

If you are using GitHub Enterprise, repeat this step for each domain (omit the api. portion). You'll also need to tell Rhubarb the root URLs:

let g:github_enterprise_urls = ['https://example.com']

How do I turn off that preview window that shows the issue body?

set completeopt-=preview

What happened to the support for hub?

Support was dropped partially because GitHub CLI appears to be unseating it as the preferred GitHub command line solution, and partially because hub isn't quite a perfect drop-in replacement for git, making life more difficult for Fugitive. My recommended solution is to call it via a Git alias:

git config --global alias.hub '!hub'

This will let you call hub pull-request via :Git hub pull-request, for example.

Like rhubarb.vim? Follow the repository on GitHub. And if you're feeling especially charitable, follow tpope on Twitter and GitHub.