I've always used git from the command line, but only recently have I started to leverage fugitive.vim to more quickly do some common git commands from within vim.
I mostly use fugitive to stage changes for committing. To stage entire
files, you can view the repository status, :Gstatus, and then navigate up
and down (k and j) tapping - next to the files to be staged (or
unstaged).
I've started to use git's interactive mode for staging changes from the
command line (git add --patch) more and more and recently wondered if the
same thing can be accomplished with fugitive.
It turns out it's pretty simple to do so. Instead of tapping - next to a
file you want to stage, you can tap p next to it and you will be
immediately dropped into interactive mode for that file. Prepare the lines
you want to stage (or, again, unstage) and save.