  Open source software projects usually acknowledge contributions with text
files, websites, and other idiosyncratic methods. These data sources are hard
to mine, which is why contributorship is most frequently measured through
changes to repositories, such as commits, pushes, or patches. Recently, some
open source projects have taken to recording contributor actions with
standardized systems; this opens up a unique opportunity to understand how
community-generated notions of contributorship map onto codebases as the
measure of contribution. Here, we characterize contributor acknowledgment
models in open source by analyzing thousands of projects that use a model
called All Contributors to acknowledge diverse contributions like outreach,
finance, infrastructure, and community management. We analyze the life cycle of
projects through this model's lens and contrast its representation of
contributorship with the picture given by other methods of acknowledgment,
including GitHub's top committers indicator and contributions derived from
actions taken on the platform. We find that community-generated systems of
contribution acknowledgment make work like idea generation or bug finding more
visible, which generates a more extensive picture of collaboration. Further, we
find that models requiring explicit attribution lead to more clearly defined
boundaries around what is and what is not a contribution.
