Fix empty path inclusion, add comments.

src/wily/commands/build.py

@@ -134,6 +134,8 @@ def build(config: WilyConfig, archiver: Archiver, operators: List[Operator]) ->
 
  # Copy the ir from any unchanged files from the prev revision
  if not seed:
+ # File names in result are platform dependent, so we convert
+ # to Path and back to str.
  files = {str(pathlib.Path(f)) for f in revision.tracked_files}
  missing_indices = files - indices
  # TODO: Check existence of file path.
@@ -156,9 +158,13 @@ def build(config: WilyConfig, archiver: Archiver, operators: List[Operator]) ->
  for deleted in revision.deleted_files:
  result.pop(deleted, None)
 
+ # Add empty path for storing total aggregates
+ dirs = [""]
+ # Directory names in result are platform dependent, so we convert
+ # to Path and back to str.
+ dirs += [str(pathlib.Path(d)) for d in revision.tracked_dirs if d]
  # Aggregate metrics across all root paths using the aggregate function in the metric
- # Note assumption is that nested dirs are listed after parent..
- dirs = {str(pathlib.Path(d)) for d in revision.tracked_dirs}
+ # Note assumption is that nested dirs are listed after parent, hence sorting.
  for root in sorted(dirs):
  # find all matching entries recursively
  aggregates = [