-Add gradio dropdown list to select checkpoints to merge

from modules import shared

CheckpointInfo = namedtuple("CheckpointInfo", ['filename', 'title', 'hash'])

CheckpointInfo = namedtuple("CheckpointInfo", ['filename', 'title', 'hash', 'model_name'])

checkpoints_list = {}

try:

    if os.path.exists(cmd_ckpt):

        h = model_hash(cmd_ckpt)

        title = modeltitle(cmd_ckpt, h)

        checkpoints_list[title] = CheckpointInfo(cmd_ckpt, title, h)

        model_name = title.rsplit(".",1)[0] # remove extension if present

        checkpoints_list[title] = CheckpointInfo(cmd_ckpt, title, h, model_name)

    elif cmd_ckpt is not None and cmd_ckpt != shared.default_sd_model_file:

        print(f"Checkpoint in --ckpt argument not found: {cmd_ckpt}", file=sys.stderr)

        for filename in glob.glob(model_dir + '/**/*.ckpt', recursive=True):

            h = model_hash(filename)

            title = modeltitle(filename, h)

            checkpoints_list[title] = CheckpointInfo(filename, title, h)

            model_name = title.rsplit(".",1)[0] # remove extension if present

            checkpoints_list[title] = CheckpointInfo(filename, title, h, model_name)

def model_hash(filename):