When pulling code from an Azure Devops repo you get the option to configure the build pipeline based off a yaml file:
However when using bitbucket as the repo, this
You dont, unfortunately. its only supported for github and azure devops repositories (at the time of writing).
https://visualstudio.uservoice.com/forums/330519-visual-studio-team-services/suggestions/33037504-yaml-bitbucket-task