The Ant-SF buildfile supplements tasks provided by the Ant-Salesforce JAR. The JAR provides a core set of tasks for retrieving and deploying metadata between Salesforce orgs and a Git version control repository.
Moreover, the buildfile supports using task branches, where each task is a separate JIRA issue. Each task (or feature) can be developed in its own Salesforce environment, and merged back into the mainline of development.
Targets are provided for both direct consulting projects and managed package products. For products, either sandboxes or trial orgs can be used with a corresponding task branch.