Have release/c/README.md link to the mirror
diff --git a/release/c/README.md b/release/c/README.md
index 73f42f8..9b45a9c 100644
--- a/release/c/README.md
+++ b/release/c/README.md
@@ -21,3 +21,15 @@
 - It will not have long term support.
 - Newer versions make no promises about compatibility.
+# Mirror
+Wuffs' canonical repository is located at
+[github.com/google/wuffs](https://github.com/google/wuffs). If you just want to
+*use* Wuffs-the-library in its C form (instead of *modifying* its Wuffs form or
+otherwise needing Wuffs-the-language tools), a mirror of just the `release/c`
+directory is located at
+By excluding everything else, the mirror is much smaller than and changes much
+less frequently than the canonical repository.