cmd/utils: fix a startup issue on deleted chaindata but dangling ancients (#27989)

core/rawdb/database.go

@@ -326,10 +326,10 @@ const (
 	dbLeveldb = "leveldb"
 )
 
-// hasPreexistingDb checks the given data directory whether a database is already
+// PreexistingDatabase checks the given data directory whether a database is already
 // instantiated at that location, and if so, returns the type of database (or the
 // empty string).
-func hasPreexistingDb(path string) string {
+func PreexistingDatabase(path string) string {
 	if _, err := os.Stat(filepath.Join(path, "CURRENT")); err != nil {
 		return "" // No pre-existing db
 	}
@@ -367,7 +367,7 @@ func openKeyValueDatabase(o OpenOptions) (ethdb.Database, error) {
 	}
 	// Retrieve any pre-existing database's type and use that or the requested one
 	// as long as there's no conflict between the two types
-	existingDb := hasPreexistingDb(o.Directory)
+	existingDb := PreexistingDatabase(o.Directory)
 	if len(existingDb) != 0 && len(o.Type) != 0 && o.Type != existingDb {
 		return nil, fmt.Errorf("db.engine choice was %v but found pre-existing %v database in specified data directory", o.Type, existingDb)
 	}