Now we can get object format name from git command line or from the
database repository table. Assume the column is right, we don't need to
read from git command line every time.
This also fixed a possible bug that the object format is wrong when
migrating a sha256 repository from external.
<img width="658" alt="image"
src="https://github.com/go-gitea/gitea/assets/81045/6e9a9dcf-13bf-4267-928b-6bf2c2560423">
b79c30435f