Vim’s :g takes two inputs: a pattern and an operation, and it runs that operation on each line that matches the pattern in the current file. :g is a tool whose usage isn’t imposed on you, nor obvious — its usefulness depends on your creativity.

Here’s an example of what :g can do: grouping related lines. Take this file:

Bundle '[email protected]:travisjeffery/IndexedSearch.git'
" Bundle 'https://github.com/Shougo/neocomplcache.git'
Bundle 'https://github.com/tpope/vim-fugitive.git'
Bundle 'https://github.com/travisjeffery/vim-help'
" Bundle 'https://github.com/Lokaltog/vim-powerline.git'
" Bundle 'https://github.com/jiangmiao/auto-pairs.git'
Bundle 'https://github.com/tpope/vim-ragtag.git'
Bundle '[email protected]:travisjeffery/vim-rails.git'
" Bundle '[email protected]:travisjeffery/vim-rails-fork.git'
Bundle 'https://github.com/tpope/vim-repeat.git'
Bundle 'https://github.com/kien/ctrlp.vim.git'
Bundle '[email protected]:travisjeffery/vim-unimpaired.git'
" Bundle 'https://github.com/thinca/vim-poslist.git'

I want the commented lines grouped and moved up top. I run:

:g/^"/m 0

And :g groups the lines. Now this is our file:

" Bundle 'https://github.com/thinca/vim-poslist.git'
" Bundle '[email protected]:travisjeffery/vim-rails-fork.git'
" Bundle 'https://github.com/jiangmiao/auto-pairs.git'
" Bundle 'https://github.com/Lokaltog/vim-powerline.git'
" Bundle 'https://github.com/Shougo/neocomplcache.git'
Bundle '[email protected]:travisjeffery/IndexedSearch.git'
Bundle 'https://github.com/tpope/vim-fugitive.git'
Bundle 'https://github.com/travisjeffery/vim-help'
Bundle 'https://github.com/tpope/vim-ragtag.git'
Bundle '[email protected]:travisjeffery/vim-rails.git'
Bundle 'https://github.com/tpope/vim-repeat.git'
Bundle 'https://github.com/kien/ctrlp.vim.git'
Bundle '[email protected]:travisjeffery/vim-unimpaired.git'

:g is one of the most underrated features in Vim. You can learn more about it by running :h :g.