Instructions for manually cherry-picking are incorrect as they do not skip merge commits

[jrhemstad]

Describe the bug

When the automatic backport fails due to conflicts in cherry-picking individual commits it will helpfully give instructions on how to manually do the cherry-pick:

git fetch origin branch/2.3.x
git worktree add -d .worktree/backport-574-to-branch/2.3.x origin/branch/2.3.x
cd .worktree/backport-574-to-branch/2.3.x
git checkout -b backport-574-to-branch/2.3.x
ancref=$(git merge-base 83b3365bbc12a9db248b67c22052413d41fae97e 9e9fb70b712a6799791997d3c70db6a28a71af72)
git cherry-pick -x $ancref..9e9fb70b712a6799791997d3c70db6a28a71af72

However, these instructions aren't correct if the PR contains merge commits as it omits the logic for filtering out merge commits.

To Reproduce
Steps to reproduce the behavior:

1. Create and merge a pull request with merge commits that also will have merge conflicts on the target branch
2. Trigger the backport workflow
3. Backport fails and comments instructions on manual cherry-picking

Expected behavior
The instructions should include how to filter out merge commits.

Workflow run logs
https://github.com/NVIDIA/cccl/actions/runs/6750303904/job/18352417643

[korthout]

That's definitely problematic and a big loss of QoL. I'll prioritize fixing this. Thanks for raising it @jrhemstad

[korthout]

Fixed in v2.1.1