Case sensitivity of Dockerfile file type?

[codeinabox]

Expected behavior

When using the vim-polygot plug-in which sets the filetype to Dockerfile no makers are set. Yet if the filetype is set to dockerfile I am able to use hadolint.

Steps to reproduce

Open a Dockerfile, run set filetype=Dockerfile and then NeomakeInfo and then compare with set filetype=dockerfile and then NeomakeInfo.

[blueyed]

I've created ekalinin/Dockerfile.vim#67 to ask for the reason of the special casing.
IIRC there have been reports/issues in this regard already.
In theory we could have a symlink or some other way to handle both, but let's wait for an answer for the above.