You can also set $GIT_PAGER/core.pager/$PAGER and create an alias to accomplish this:

  #export PAGER='less -SEXIER'
  #export GIT_PAGER='less -SEXIER'
  git config --global core.pager 'less -SEXIER'
  git config --global alias.l 'log --graph --oneline --decorate --color'
  # git diff ~/.gitconfig
  git l

core.pager: https://git-scm.com/docs/git-config#Documentation/git-config...

> The order of preference is the $GIT_PAGER environment variable, then core.pager configuration, then $PAGER, and then the default chosen at compile time (usually less).