ControllerLinkBuilder do not take into account path extensions in generated links

The ControllerLinkBuilder do not take into account the path extension if this is used instead of specifying the requested format using a Accept header.

Given the request mapping "/path/entity/{id}" and springs content-negotiation configured to support both Accept header and path-extensions, I would expect that the links generated for the response when accessing the URL with a path extension actually includes the path extension in the links created by ControllerLinkBuilder. This is not the case. Is this by design? I understand that links/uris identifying resources should be unaware of content-types, but in the context of a request using path extensions it would be more practical if the client could navigate the links without manually appending the path extension.

For example would the response to the request "/path/entity/123.json" include a self-rel link to "/path/entity/123", forcing the client to manually add the .json extension for the link to be usable in the current context of the client.

Start at ControllerLinkBuilder and trace how links are generated for requests using path extensions versus Accept headers. Compare the generated link with the request URI in the example, then determine and document the expected behavior for path-extension links; no test or source file is named in the issue.