prow/plugins/approve/approvers/owners.go
func (o Owners) removeSubdirs(dirs sets.String) {
	canonicalize := func(p string) string {
		if p == "." {
			return ""
		}
		return p
	}
	for _, dir := range dirs.List() {
		path := dir
		for {
			if o.repo.IsNoParentOwners(path) || canonicalize(path) == "" {
				break
			}
			path = filepath.Dir(path)
			if dirs.Has(canonicalize(path)) {
				dirs.Delete(dir)
				break
			}
		}
	}
}
func (o Owners) removeSubdirs(dirs sets.String) {
	canonicalize := func(p string) string {
		if p == "." {
			return ""
		}
		return p
	}
	for _, dir := range dirs.List() {
		path := dir
		for {
			if o.repo.IsNoParentOwners(path) || canonicalize(path) == "" {
				break
			}
			path = filepath.Dir(path)
			if dirs.Has(canonicalize(path)) {
				dirs.Delete(dir)
				break
			}
		}
	}
}
// removeSubdirs takes a set of directories as an input and removes all subdirectories.
// E.g. [a, a/b/c, d/e, d/e/f] -> [a, d/e]
// Subdirs will not be removed if they are configured to have no parent OWNERS files or if any
// OWNERS file in the relative path between the subdir and the higher level dir is configured to
// have no parent OWNERS files.