I have read How to move files from one git repo to another (not a clone), preserving history
My dir:
➜  website git:(master) tree
.
├── README.md
├── sub-dir-1
│   ├── file1
│   └── file2
├── sub-dir-2
│   └── file3
I can move sub-dir-1 to another repo and save its git history log.
But I want to move README.md to another repo which save git history log, because README.md is old repo root file which isn't sub dir.
So, how should I do? thanks!
EDIT: solved according to Splitting a set of files within a git repo into their own repository, preserving relevant history
