updated make docs

rig/docs/notes/docs.md

@@ -18,3 +18,12 @@ fails. The pages declare an empty icon, so the browser does not ask for a
 
 Rendered SVGs are committed alongside their `.dot` sources for the same reason:
 the pages have to read on a machine with no Graphviz installed.
+
+## Whose docs
+
+`make docs` serves the docs of the folder it runs from. In rig that is rig's own `docs/`. A
+project's launcher sets `DOCS_DIR` to its own `docs/` (an absolute path), so `make docs` there
+serves the project's pages through this same script, on the same terms: an `index.html` at
+the top, the environment's block for the port (`HTTP_PORT + 4`), a container named after the
+environment. rig's own docs stay one `make -C <rig> docs` away. The project keeps no copy of
+this script.