1. A system comprising: a processor programmed to initiate executable operations comprising: responsive to receiving a request to create a placeholder for a reusable artifact representing a reusable unit, creating the placeholder for an appropriate version of the reusable artifact within a container and assigning a first parameter identifying the reusable artifact to an artifact property of the placeholder, wherein the placeholder further comprises a branch property configured to indicate a first null value or a second parameter identifying a branch of the reusable artifact corresponding to a particular variant of the reusable artifact, and a version property configured to indicate a second null value or a third parameter identifying a particular version of the reusable artifact; responsive to receiving a request to pin a particular version of the reusable artifact to the placeholder, updating a version property of the placeholder to set the version, wherein the request to pin is implemented by assigning a value to a parameter in the placeholder or adding a pin property into the placeholder; and maintaining the particular version as the set version of the reusable artifact regardless of whether new artifact versions are created for the reusable artifact.