When using gh stack link to open new PRs in an existing stack, the default PR titles were not what I expected

[dyc3]

I had a stack that I was using graphite originally with, and was using the link command to submit new PRs. It created the PR with the title using the branch name (ex. dyc3/yaml-fmt-explicit-entries). I'm used to the behavior of gh pr create, where t if there's only one commit in the branch, the default title is my commit's message. I was expecting the same behavior for the link command.