There was only one `IsRepositoryExist` function, it did: `has && isDir`
However it's not right, and it would cause 500 error when creating a new
repository if the dir exists.
Then, it was changed to `has || isDir`, it is still incorrect, it
affects the "adopt repo" logic.
To make the logic clear:
* IsRepositoryModelOrDirExist
* IsRepositoryModelExist