Update doc/note/auto-formatting.md for dumbindent
diff --git a/doc/note/auto-formatting.md b/doc/note/auto-formatting.md
index ad9470a..947c156 100644
--- a/doc/note/auto-formatting.md
+++ b/doc/note/auto-formatting.md
@@ -1,7 +1,11 @@
# Auto-Formatting
Within this repository:
-- `C` code is formatted by `clang-format-5.0 -style=Chromium`.
+- Hand-written `C` code is formatted by `clang-format-5.0 -style=Chromium`.
+- Auto-generated `C` code is formatted by [`dumbindent`](/cmd/dumbindent),
+ which isn't as 'pretty' in some sense, but is [substantially
+ faster](https://github.com/google/wuffs/blob/a0f7059eeb022c4dec70ffae4041bcc54f666c0d/cmd/dumbindent/main.go#L32-L44),
+ making the edit-compile-run cycle more productive.
- `Go` code is formatted by `gofmt`.
- `Wuffs` code is formatted by [`wuffsfmt`](/cmd/wuffsfmt).
