Failure when adding a file to a directory name only

[John-K]

The following fails, when it should just add a file to the directory:
./fatboy test.bin mkdir a
./fatboy test.bin add fatboy a

this also fails:
./fatboy test.bin add fatboy a/

this does what's expected:
./fatboy test.bin add fatboy a/fatboy

We should detect these errors, check if the target is a directory, and auto-fix the parameters to make it work.