Git Workflow: do not use just the filename, but full path in reporting

[david-binda]

Changes the runGitWorkflowForFile the way it uses the passed in path for a file, instead of just the filename, during reporting in order to fix the incorrectly reported issues in new files with same filename, but different paths.

A test covering the edge case is also included.

fixes #104

[sirbrillig]

This looks amazing! Thanks for the bug fix. I just want to go over the commit history once to make sure I understand why we used the filename in this code to begin with. It seems like a very intentional decision so I want to make sure we're not breaking something.

[sirbrillig]

It looks like getFileNameFromPath was added in #54, specifically 14c8138 and 1039133. I can't quite tell why it was there except as a replacement for the previous use of DiffLineMap::getFileNameFromDiff() which seems to return whatever the full filename is in the diff; it's not clear to me why we needed to switch to the relative filename there.

The filename requirement seems to be added in #51 originally, and that also has tests (thanks for those!) so hopefully this won't break those optimizations either.

The only request I have, then is that we make this improvement to both the svn and the git workflows and remove getFileNameFromPath entirely since I believe this is its only use.

[sirbrillig]

@david-binda if you'd prefer, we can just merge this fix since it's an important bug and handle cleaning up the SVN version later. What do you think?

[sirbrillig]

Still waiting for a reply but I think I'm going to merge this anyway as it fixes a present bug.