manifest.go
func openOrCreateManifestFile(dir string, readOnly bool) (ret *manifestFile, result Manifest, err error) {
	return helpOpenOrCreateManifestFile(dir, readOnly, manifestDeletionsRewriteThreshold)
}
func openOrCreateManifestFile(dir string, readOnly bool) (ret *manifestFile, result Manifest, err error) {
	return helpOpenOrCreateManifestFile(dir, readOnly, manifestDeletionsRewriteThreshold)
}
// openOrCreateManifestFile opens a Badger manifest file if it exists, or creates on if
// one doesn’t.