shellenv: improve --help formatting.
shellenv: improve --help formatting.

EricFromCanada/brew,claui/brew,EricFromCanada/brew,JCount/brew,mahori/brew,Homebrew/brew,reitermarkus/brew,nandub/brew,sjackman/homebrew,sjackman/homebrew,sjackman/homebrew,konqui/brew,sjackman/homebrew,nandub/brew,claui/brew,mahori/brew,claui/brew,mahori/brew,reitermarkus/brew,reitermarkus/brew,claui/brew,Homebrew/brew,konqui/brew,Homebrew/brew,reitermarkus/brew,nandub/brew,MikeMcQuaid/brew,EricFromCanada/brew,JCount/brew,konqui/brew,JCount/brew,vitorgalvao/brew,JCount/brew,nandub/brew,vitorgalvao/brew,MikeMcQuaid/brew,mahori/brew,vitorgalvao/brew,MikeMcQuaid/brew,EricFromCanada/brew,vitorgalvao/brew,konqui/brew,MikeMcQuaid/brew,Homebrew/brew