command generate should only scan source directory if path has trailing slash

[Ghifari160]

Command generate detects if the source path is a directory, and scans its contents if it is. This was done so running migrate generate . destination would create map the current directory contents to destination. However, running migrate generate source destination would map the contents of source (rather than source itself) to destination. This might not be preferable. Ideally, running that command maps source itself to destination. To map the contents of source, a trailing slash can be added (i.e. source/). . can be treated as a special exception to preserve the default behavior.