expand README a bit

README.md

@@ -3,7 +3,7 @@
 This repository contains the shared Iris CI. It contains common code for Iris
 projects' CI.
 
-Projects automatically use the latest commit of some branch for their CI, so
+Projects automatically use the latest commit of *some branch* for their CI, so
 branches should remain reasonably compatible.  Every branch here comes with a
 corresponding branch [in the Docker repo](https://github.com/RalfJung/opam-ci),
 providing the Docker image that should be used.  Currently, we have the
@@ -11,6 +11,9 @@ following branches:
 
 * [`opam2`](https://gitlab.mpi-sws.org/FP/iris-ci/tree/opam2), using opam 2.0.
 
+Pushing to `master` here will not be picked up by the projects, always remember
+to also push to the right branch!
+
 ## How to configure CI for your project
 
 First of all, your project needs to have a CI runner.  We have two runners