If you use version control systems like Git or Mercurial and you use Vim to edit your source files, then you might find the Signify plugin very useful. When you edit a version controlled file, Signify shows which lines are changed using signs (or markers) in the gutter on the left side.
Signify can be installed using your favorite plugin manager from: https://github.com/mhinz/vim-signify
By default, Signify works with a large number of version controls systems. If you only use one or a few of those, then you can speed up Signify a bit by informing it to only check those VCS. For example, I only use Git and Mercurial, so I add this line to my vimrc:
let g:signify_vcs_list = [ 'git', 'hg' ]
let g:signify_sign_delete = "-"
Tried with: Vim 7.4 and Ubuntu 16.04