org.apache.sis.referencing.operation.transform.TransformSeparator is Apache SIS 0.8 unconditionally keep all source dimensions, unless the source dimensions to keep were explicitly specified. The behavior should be changed by removing all dimensions that are not needed for the target dimensions to keep.
In a milestone toward SIS 1.0, we added a setTrimSourceDimensions(boolean) method. However in practice this flag is always false if source dimensions were explicitly specified. So we propose to remove that flag and instead have the behavior selected automatically depending on whether source dimension were specified or not. It makes the API simpler, by providing better symmetry with the behavior regarding target dimensions.
This is a slightly incompatible change since we are changing the behavior of TransformSeparator when no source dimensions is specified. However we believe that the new behavior is closer to the expected one in such situation.