Describe the feature or problem you’d like to solve

gh pr create --fill has a good default if you only have a single commit: it creates a PR with the commit's details as title/description. However I generally write my first commit's message knowing that it will be used as the PR title/desc and will have follow-up commits that I expect will be squashed at some point. When using gh pr create --fill when there are multiple commits, it uses the branch name as PR title and the list of git commit titles as the PR description.

Proposed solution

Add a CLI option that will always fill the PR title/description using only the first commit's message. This won't disrupt the default and helps support a different and reasonable workflow.