For backwards-compatibility reasons we'll have to keep around a Header.Write, of course.

CL https://golang.org/cl/25341 mentions this issue.

Copy of comment from CL:

Do we really want to add a WriteSubset method to the textproto package? It's weird enough in net/http in retrospect. If textproto needs this functionality, then I'd rather move the bulk of the logic to an internal shared package so we don't need to expose WriteSubset.

So the idea would be to add WriteSubset to net/internal?

Another solution would be to implement Write without WriteSubset in textproto, and keep the WriteSubset implementation in http.

As long as we don't add more public API.

Let's leave things alone for Go 1.8.

Looks like the CL https://go-review.googlesource.com/c/go/+/25341/ was abandoned with a reasoning of we don't want to make the change, cc @rsc

The CL doesn't mention any NACK. Brad said we shouldn't expose WriteSubset, but that doesn't mean the CL is rejected.

@emersion, @rsc replied with

The author has not replied since PS1 when I asked him/her to update the Author and Committer lines, and also we don't believe we want to do this. So -2 and abandoning.

That was my direct reading of the abandonment.

Also adding that method without a proposal is no longer feasible, so I am going to repurpose this issue as a proposal that’ll go through a review.

I have no longer interest in this.