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, potentially overriding the requirements of the target.

NewBuildListError returns a new BuildListError wrapping an error that occurred at a module found along the given path of requirements and/or upgrades, which must be non-empty.

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.