Add tests of CloneCommand implementations

The CliGit and JGit implementations are different as noted in the
comments of the test methods.

Refer to the comments in the source file for some of the difference
detected by the tests.
If CloneCommand base object has repository, close it at end of execute()
Attempt to close repo opened by fetch, hoping to close another file

Desparately need a unit test oriented way to identify the stack trace
of the code which opened a file so that the test failure can be
assigned to a specific stack trace.