$ git config --get-regexp '^alias\.'
alias.st status
alias.br branch
alias.co checkout
alias.ci commit

#heck, you could even alias that

$ git config --global alias.listalias 'config --get-regexp '^alias\.''

#and call it like

$ git listalias
alias.st status
alias.br branch
alias.co checkout
alias.ci commit
alias.listalias config --get-regexp ^alias.