describe current status in CONTRIBUTING.md file

PiperOrigin-RevId: 707546656
Change-Id: I88eaae698e622a2e2b2bc0f4d57fd1eef8bd98f7
Reviewed-on: https://go-review.googlesource.com/c/open2opaque/+/637377
Reviewed-by: Michael Stapelberg <stapelberg@google.com>
Auto-Submit: Michael Stapelberg <stapelberg@google.com>
Reviewed-by: Chressie Himpel <chressie@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

CONTRIBUTING.md

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index b16bd94..1679cd1 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,6 +1,12 @@
 # How to contribute
 
-We'd love to accept your patches and contributions to this project.
+This repository is an export of a Google-internal repository.
+
+We are currently not well set up to accept contributions, but are looking into it.
+
+If you want to suggest a code change, you can send it via [GitHub pull
+requests](https://help.github.com/articles/about-pull-requests/). We can then
+apply it internally and release it (but not merge your pull request directly).
 
 ## Before you begin
 
@@ -23,11 +29,3 @@
 This project follows
 [Google's Open Source Community Guidelines](https://opensource.google/conduct/).
 
-## Contribution process
-
-### Code reviews
-
-All submissions, including submissions by project members, require review. We
-use GitHub pull requests for this purpose. Consult
-[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
-information on using pull requests.