There should be sanity checks for jekyll import:

$ hugo import jekyll . .

WARNING: This will overwrite config in current directory and create a messy directory tree.

For instance this should not be allowed (it creates a very deep structure as it reads its own output).

The import should verify that

1. the source directory looks like a valid jekyll install (look for config maybe? fail if no posts are found?
2. target directory is empty or doesn't exist (create it)