BuildList returns the build list for the target module.

Downgrade returns a build list for the target module in which the given additional modules are downgraded.

Req returns the minimal requirement list for the target module, with the constraint that all module paths listed in base must appear in the returned list.

Upgrade returns a build list for the target module in which the given additional modules are upgraded.

UpgradeAll returns a build list for the target module in which every module is upgraded to its latest version.

BuildListError decorates an error that occurred gathering requirements while constructing a build list.

A Reqs is the requirement graph on which Minimal Version Selection (MVS) operates.