If you look around, there are higher priority issues that stick around for years without a resolution. My advice: either learn Jenkins development and submit a PR implementing what you want, or find alternative options.
In my case, I made a Jenkins Shared Library with the stuff I commonly use. One of them is a script that includes git cloning, with various options that I needed. I uploaded it here: https://gist.github.com/gene-pavlovsky/dcb93598f46ae0b512dff7f5c0088f32
Example usage:
gitScript.checkoutRepo(remoteUrl: gitUrl, targetDir: repoDir, branches: [ 'master', branch ], cloneMode: 'treeless')
Yeah, it would be nice to have built-in support for this feature. For now, I'm doing it by manually calling `git` commands in a `sh` step, the following example partially clones the repo, checks out SOME_BRANCH, merges master into it, and pushes: