Git with Vimdiff

One time view:

git difftool --tool=vimdiff --no-prompt <filename>

Always:

git config --global diff.tool vimdiff
git config --global merge.tool vimdiff

For Single Repository:

git config diff.tool vimdiff
git config merge.tool vimdiff

To avoid having Git prompt when launching Vimdiff:

git config --global difftool.prompt false