You use git and you write your commit messages in vim.
You like to see the changes you staged while you write your comment.
If that's the case you can add this line to your vimrc
autocmd FileType gitcommit DiffGitCached | wincmd J
That tells vim to run the command
wincmd J when opening the filetype
gitcommit. As you can imagine the
DiffGitCached command opens a buffer to show the
git diff --cached output.
wincmd J is there just to moves the panel on the right-hand side.
Original source Stackoverflow