Refactor `formula_at_revision`.
Refactor `formula_at_revision`.

Linuxbrew/brew,vitorgalvao/brew,reelsense/brew,amar-laksh/brew_sudo,Homebrew/brew,vitorgalvao/brew,alyssais/brew,DomT4/brew,Homebrew/brew,jmsundar/brew,sjackman/homebrew,MikeMcQuaid/brew,aw1621107/brew,MikeMcQuaid/brew,zmwangx/brew,nandub/brew,MikeMcQuaid/brew,Linuxbrew/brew,maxim-belkin/brew,Homebrew/brew,nandub/brew,gregory-nisbet/brew,EricFromCanada/brew,amar-laksh/brew_sudo,claui/brew,konqui/brew,palxex/brew,claui/brew,mgrimes/brew,reelsense/brew,amar-laksh/brew_sudo,sjackman/homebrew,alyssais/brew,sjackman/homebrew,JCount/brew,nandub/brew,reitermarkus/brew,vitorgalvao/brew,gregory-nisbet/brew,JCount/brew,mahori/brew,palxex/brew,bfontaine/brew,pseudocody/brew,sjackman/homebrew,zmwangx/brew,palxex/brew,mahori/brew,muellermartin/dist,pseudocody/brew,hanxue/linuxbrew,vitorgalvao/brew,konqui/brew,aw1621107/brew,konqui/brew,EricFromCanada/brew,JCount/brew,MikeMcQuaid/brew,mgrimes/brew,ilovezfs/brew,claui/brew,JCount/brew,jmsundar/brew,reitermarkus/brew,zmwangx/brew,mahori/brew,DomT4/brew,jmsundar/brew,aw1621107/brew,maxim-belkin/brew,muellermartin/dist,claui/brew,DomT4/brew,hanxue/linuxbrew,Linuxbrew/brew,bfontaine/brew,reitermarkus/brew,reelsense/brew,mgrimes/brew,hanxue/linuxbrew,Homebrew/brew,bfontaine/brew,konqui/brew,EricFromCanada/brew,ilovezfs/brew,Linuxbrew/brew,reitermarkus/brew,nandub/brew,pseudocody/brew,mahori/brew,maxim-belkin/brew,muellermartin/dist,ilovezfs/brew,EricFromCanada/brew,gregory-nisbet/brew,DomT4/brew,alyssais/brew