*/Dockerfile: add header with short description

Author: crasbe

murdock-worker/Dockerfile

@@ -1,4 +1,3 @@
-#
 # RIOT Murdock Dockerfile
 #
 # the resulting image is being used in RIOT's CI (Murdock)

riotbuild/Dockerfile

@@ -1,24 +1,8 @@
+# `riotbuild` Dockerfile
 #
-# RIOT Dockerfile
-#
-# The resulting image will contain everything needed to build RIOT for all
-# supported platforms. This is the largest build image, it takes about 1.5 GB in
-# total.
-#
-# Setup:
-# 1. Install docker, add yourself to docker group, enable docker, relogin
-#
-# Use prebuilt image:
-# 1. Prebuilt image can be pulled from Docker Hub registry with:
-#      # docker pull riot/riotbuild
-#
-# Use own build image:
-# 1. Build own image based on latest base OS image (from the riotbuild directory):
-#      # docker build --pull -t riotbuild .
-#
-# Usage:
-# 1. cd to riot root
-# 2. # docker run -i -t -u $UID -v $(pwd):/data/riotbuild riotbuild ./dist/tools/compile_test/compile_test.py
+# This container includes the whole build toolchain required to build all
+# platforms supported by RIOT.
+
 ARG DOCKER_REGISTRY="docker.io/riot"
 FROM ${DOCKER_REGISTRY}/static-test-tools:latest
 

riotdocker-base/Dockerfile

@@ -1,3 +1,8 @@
+# `riotdocker-base` Dockerfile
+#
+# This container sets the foundation for all subsequent containers and
+# initializes the user environment.
+
 FROM ubuntu:jammy
 
 LABEL maintainer="Kaspar Schleiser <kaspar@riot-os.org>"

static-test-tools/Dockerfile

@@ -1,3 +1,8 @@
+# `static-test-tools` Dockerfile
+#
+# This container has all the dependencies required to execute the static tests
+# for the RIOT sources.
+
 ARG DOCKER_REGISTRY="docker.io/riot"
 FROM ${DOCKER_REGISTRY}/riotdocker-base:latest