Wrong 'git mv', dir. hierarchy fix [87757] and new -t/trial_run option

This branch includes a fix for the bug I reported at: https://rt.cpan.org/Public/Bug/Display.html?id=87757 (and also brought up in the discussion of bug https://rt.cpan.org/Public/Bug/Display.html?id=87172).  The branch also includes changes to implement a -t (trial_run - report, no changes) option.  I find this option quite helpful - and I suspect others will also - to check if a module-rename command I'm considering will do what I expect it to do before I actually execute it.  I've tested the changes by hand and found no problems.  Unfortunately, I don't have time (at least currently) to write automated tests for these changes.