What command will get the latest version of plugins in Terraform that complies with the configuration's version constraints?

The command that retrieves the latest version of plugins in Terraform, which satisfies the version constraints specified in the configuration, is the upgrade command. This command is specifically designed to check the current state of provider plugins and upgrade them to their latest compatible versions, as dictated by the constraints defined in the Terraform configuration files.

Using the upgrade command ensures that all plugins are not only updated to the latest version but also remain within the bounds of compatibility specified by the user. This is crucial for maintaining stability in your infrastructure while also enabling the use of newer features and improvements.

The other commands listed do not function in the same way. For instance, an update command typically does not exist in Terraform's context; it might imply a generic update but does not specifically manage plugin versions. Similarly, update-plugins and get-plugins are not valid Terraform commands, which highlights their ineffectiveness in this scenario. Only the upgrade command appropriately reflects the required functionality for managing plugin versions according to set constraints.