Inconsistent symlink handling

### How to Reproduce
- Create a file x.tsv
- Create a symlink y.tsv to x.tsv
- Use mcmd to import y.tsv

### Expected behavior
```
✖ Importing y.tsv
  Unknown entity type 'y'.
```
less expected but also valid:
```
✖ Importing x.tsv
  Unknown entity type 'x'.
```
### Observed behavior
```
✖ Importing y.tsv
  Unknown entity type 'x'.
```