CI: improve README.md

Our "debian-buster" CI image was clearly not a buster
(based on versions in logs).  I suspect this change can help.

diff --git a/ci/README.md b/ci/README.md
index fdc7b9fe12d22e753264af9a298cd0b41e633ced..8bd70a24b75ce168da1d4d5788424c4c9544ef19 100644 (file)
--- a/ci/README.md
+++ b/ci/README.md
@@ -1,12 +1,11 @@
 Docker Build
 ------------
 
-* debian-buster
-
 ```
-$ export KNOT_BRANCH=3.0
-$ docker build --no-cache -t registry.nic.cz/knot/knot-resolver/ci/debian-buster:knot-$KNOT_BRANCH --build-arg KNOT_BRANCH=$KNOT_BRANCH debian-buster
+$ export DISTRO=debian-buster # also debian-11
+$ export KNOT_BRANCH=3.0 # also master
+$ docker build --no-cache -t registry.nic.cz/knot/knot-resolver/ci/$DISTRO:knot-$KNOT_BRANCH --build-arg KNOT_BRANCH=$KNOT_BRANCH $DISTRO
 
 $ docker login registry.nic.cz
-$ docker push registry.nic.cz/knot/knot-resolver/ci/debian-buster:knot-$KNOT_BRANCH
+$ docker push registry.nic.cz/knot/knot-resolver/ci/$DISTRO:knot-$KNOT_BRANCH
 ```