No overlay - Remove files that appear in the index and working tree, but not in tree-ish.
Create reflog - to doCreate the new branch’s reflog
Ignore other worktrees - to doAllow checkout when the commit is already checked out to another working folder
Ignore skip worktree bits - to doIgnore any the sparse checkout patterns
Quiet - to doSuppress all output.
For more information on adding files to git, see the git checkout command line documentation.