Generic git diff alias for merge-base

Question

I'm looking to create an alias that takes a diff between the merge base of a branch and origin/HEAD. Ideally, I'd be able to write something like:

[alias]
  hd = diff origin/HEAD...

however, that ends up being expanded out to this:

git diff origin/HEAD... branchname

The problem there is the space between ... and branchname causes a different result than I'm looking for. I can invoke this as:

[alias]
  hd = "!git diff origin/HEAD...$@"

and get what I'm looking for, however, that breaks things like --name-only for:

git hd --name-only

unless I explicitly write HEAD and put the arguments later:

git hd HEAD --name-only

Is there a way to write this alias that works and still allows for typical ordering of flags?

It looks like something hd = diff --merge-base origin/HEAD would probably work, but I'm stuck on 2.25, currently.