fix: added/deleted lines is incorrect

[ctlai95]

Problem

FsWrite card always shows +0 -0 for diff changes. This is happening because we aren't comparing with the old content before the tool executed.

Solution

• Refactor fsWrite to move out all the logic relating to getting the contents before/after the change
• Ensure we are always comparing with the old content (we are now storing this in a tool lookup map)
• Fixed an issue where openDiff did not work for nested file paths because relative file path was not used
  

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.