The unsafeDiffAtPaths function calls diff_at_path for a set of files and
and directories, and returns all changes to those files. It recurses into
given directories when searching for changes.
Comparing paths and not slurpies is useful when the user
requests a diff for a file that is created or removed in the working copy:
then there is no slurpy for the file in the current or working slurpy
The given paths must always be fixed repository paths starting with a
.. It is safe to pass overlapping paths.
The booleans in the first argument tell whether to ignore mtimes, whether
we must look for additions and if we're diffing for a summary only.
It returns an FL of patches, that contains all the changes that have been
made at all those paths.