refactor: improve the logic for indent of a level

refactor: improve the logic for indent of a level

refactor: improve the logic for indent of a level

refactor: improve the logic for indent of a level

feat: improve the logic for save_fold_end_line again

feat: improve the logic for save_fold_end_line again

test: move testcase to single file

test: more tests

feat: improve the logic for save_fold_end_line

feat: improve the logic for save_fold_end_line

perf: caculate sign char only once

fix: no sign for one line fold

fix: no sign for one line fold

fix: not line for one line fole

test: continue moving testcase to single file

test: continue moving testcase to single file

fix: end line of a fold is a closed sub fold again

fix: end line of a fold is a closed sub fold again

fix: correct some test cases

fix: correct some test cases

fix: end line of a fold is a closed sub fold

fix: end line of a fold is a closed sub fold

fix: end line of current fold is a closed fold should be highlighted

test: more tests

test: move testcase to single file

test: move testcase to single file

refactor: rewrite the logic for fold_line_char_open_{start,end}_close…

fix: closed subfold fallback char is not right

fix: closed subfold will highlight other folds

fix: fallback to previous fold will effect other folds