proposal: archive/tar: add iterator form of (&Reader).Next()

[sivchari]

Proposal Details

In Go 1.23, we can use range-over-func a.k.a iterator and developers propose to apply for the package into some packages.

For instance, the following issues are easy to know what kind of content are proposed.
#61897
#64341

This proposal is similar with above it.
I think it's good to apply for archive/tar, too.

func (tr *Reader) NextIter() iter.Seq2[*Header, error] {
	return func(yield func(*Header, error) bool) {
		hdr, err := tr.Next()
		if err == io.EOF {
			return
		}
		if !yield(hdr, err) {
			return
		}
	}
}

Thanks.

[ianlancetaylor]

Perhaps AllHeaders would be a better name.

Also I think error handling for this sort of iterator is currently an open issue. We may want to wait a bit to see if we come to a consensus on iterators where each value can fail.

[robpike]

I think that the question of adding iterators to existing packages is an example of what I was talking about in #67510