Updates to support HECKformat documents, and minor changes.

- Update copyright.
- Remove manifest.in since we're switching to PDM (and defaults moved
  to the module).
- Remove setup.py since we're switching to PDM.
- Remove chains.yaml, move data to the processor module.
- Fix passthrough in __main__
- Move main function to separate function to support PDM entrypoint.
- metadata.py: Extensive rework
  * Add heck support (lots of little changes to support it). (.heck files can
    replace .meta files)
  * Add yaml metadata support (.meta files can be yaml)
  * Some formatting changes.
  * Make metatree be a little easier to read by separating out
    functionality into extra functions
- processchain.py: Move chains.yaml to a structure internal.
- Add processors/process_heck.py to support the document side of HECKformat
- add pyproject.toml and embrace PDM.

heckweasel/__main__.py

@@ -15,7 +15,7 @@ from typing import Dict, List, cast
 
 from .metadata import MetaTree
 from .processchain import ProcessorChains
-from .processors.processors import PassthroughException
+from .processors.processors import PassthroughException, NoOutputException
 from .pygments import pygments_get_css, pygments_markup_contents_html
 from .template_tools import (
     date_iso8601,
@@ -144,14 +144,23 @@ def main() -> int:
             print("process {} -> {} -> {}".format(os.path.join(root, f), repr(chain), os.path.join(target_dir, chain.output_filename)))
             if not args.dry_run:
                 try:
+                    # normal output
+                    # FIXME support binary streams
+                    collected_output = [line for line in chain.output]
                     with open(os.path.join(target_dir, chain.output_filename), "w") as outfile:
-                        for line in chain.output:
-                            outfile.write(line)
+                        outfile.writelines(collected_output)
                 except PassthroughException:
+                    # write output from input
                     shutil.copyfile(os.path.join(root, f), os.path.join(target_dir, chain.output_filename))
+                except NoOutputException:
+                    print("skip output {} -> {}".format(os.path.join(root, f), os.path.join(target_dir, chain.output_filename)))
+                    # don't write anyp output
+                    pass
 
     return 0
 
+def do_main():
+    sys.exit(main())
 
 if __name__ == "__main__":
-    sys.exit(main())
+    do_main()