ci: Document how to build the image

Updating the CI image is rare enough to not know the involved
commands by heart, so adding a comment like mutter did a while
ago makes perfect sense.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1177

diff --git a/.gitlab-ci/Dockerfile b/.gitlab-ci/Dockerfile
index 6ec6aff9f20bfb7bdb76fe9a11959d2f85fb753f..4c7f1097d2f9078142a52e3dfe6e21c74df11bbb 100644 (file)
--- a/.gitlab-ci/Dockerfile
+++ b/.gitlab-ci/Dockerfile
@@ -1,3 +1,10 @@
+# Rebuild and push with
+#
+#     cd .gitlab-ci/
+#     podman build --format docker --no-cache -t registry.gitlab.gnome.org/gnome/gnome-shell/extension-ci:v1 .
+#     podman push registry.gitlab.gnome.org/gnome/gnome-shell/extension-ci:v1
+#
+
 FROM registry.fedoraproject.org/fedora:latest
 
 RUN dnf -y update && dnf -y upgrade && \