Like this question , git-config does not support variable expansion, however you can define an alias with common parts:
lg = log --graph --pretty=format:'%C(cyan)%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(red)<%an>%Creset' --abbrev-commit --date=relative
Then define additional aliases as shell commands that use a common alias:
unreleased = !git --no-pager lg release..master
, --date=relative , %cr . , --date=short, , . %cd , , .