circleci: Create script for generating Dockerfiles.

[greg: updated Dockerfile comment]

.gitignore

@@ -29,6 +29,9 @@ package-lock.json
 /.vagrant
 /var
 
+# Dockerfiles generated for CircleCI
+/tools/circleci/images
+
 # Static build
 *.mo
 npm-debug.log

tools/circleci/Dockerfile.template

@@ -1,4 +1,5 @@
-# Dockerfile for a generic Ubuntu 14.04 image with just the basics we need
+{generated_file_warning}
+# Dockerfile for a generic Ubuntu image with just the basics we need
 # to make it suitable for CI.  In particular:
 #  * a non-root user to run as (a pain to try to do in setup,
 #    because by then we've already cloned the repo);
@@ -20,14 +21,15 @@
 # (but much simpler, with a couple of packages from the distro), and
 # then borrows from the CircleCI Dockerfile.
 
-# To rebuild from this file:
-#   0. pick a new image name, like `gregprice/circleci:trusty-python-3.test`
-#   1. $ sudo docker build tools/circleci/images/ --tag $NAME
-#   2. $ sudo docker push $NAME
-#   3. update .circleci/config.yml to refer to the new name
+# To rebuild from this file for a given release, say trusty:
+#   0. $ tools/circleci/generate-dockerfiles
+#   1. pick a new image name, like `gregprice/circleci:trusty-python-3.test`
+#   2. $ sudo docker build tools/circleci/images/$RELEASE/ --tag $NAME
+#   3. $ sudo docker push $NAME
+#   4. update .circleci/config.yml to refer to the new name
 
 # TODO add xenial
-FROM buildpack-deps:trusty-scm
+FROM {base_image}
 
 RUN echo 'APT::Get::Assume-Yes "true";' > /etc/apt/apt.conf.d/90circleci \
   && echo 'DPkg::Options "--force-confnew";' >> /etc/apt/apt.conf.d/90circleci
@@ -40,7 +42,7 @@ RUN apt-get update \
     netcat unzip zip jq \
     python3-pip \
   && ln -sf /usr/share/zoneinfo/Etc/UTC /etc/localtime \
-  && { locale-gen en_US.UTF-8 || true; } \
+  && {{ locale-gen en_US.UTF-8 || true; }} \
   && echo "LC_ALL=en_US.UTF-8" | sudo tee -a /etc/default/locale
 
 # Set the locale, together with the locale-related steps above.
@@ -61,9 +63,9 @@ ENV LC_ALL en_US.UTF-8
 # Docker core...
 RUN set -e \
   && export DOCKER_VERSION=$(curl --silent --fail --retry 3 https://download.docker.com/linux/static/stable/x86_64/ | grep -o -e 'docker-[.0-9]*-ce\.tgz' | sort -r | head -n 1) \
-  && DOCKER_URL="https://download.docker.com/linux/static/stable/x86_64/${DOCKER_VERSION}" \
+  && DOCKER_URL="https://download.docker.com/linux/static/stable/x86_64/${{DOCKER_VERSION}}" \
   && echo Docker URL: $DOCKER_URL \
-  && curl --silent --show-error --location --fail --retry 3 --output /tmp/docker.tgz "${DOCKER_URL}" \
+  && curl --silent --show-error --location --fail --retry 3 --output /tmp/docker.tgz "${{DOCKER_URL}}" \
   && ls -lha /tmp/docker.tgz \
   && tar -xz -C /tmp -f /tmp/docker.tgz \
   && mv /tmp/docker/* /usr/bin \

tools/circleci/generate-dockerfiles

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+
+import errno
+import os
+
+import yaml
+
+def generate_dockerfile_directories(dockerfile_path: str) -> None:
+    if not os.path.exists(os.path.dirname(dockerfile_path)):
+        try:
+            os.makedirs(os.path.dirname(dockerfile_path))
+        except OSError as e:
+            if e.errno != errno.EEXIST:
+                raise
+
+if __name__ == "__main__":
+    os.chdir(os.path.abspath(os.path.dirname(__file__)))
+
+    with open("Dockerfile.template") as f:
+        docker_template = f.read()
+
+    with open("images.yml") as f:
+        dockerfile_settings = yaml.safe_load(f)
+
+    for distro in dockerfile_settings:
+        dockerfile_settings[distro]["generated_file_warning"] = """\
+# THIS IS A GENERATED FILE. DO NOT EDIT.
+# See template: tools/circleci/Dockerfile.template
+"""
+
+        dockerfile_content = docker_template.format_map(dockerfile_settings[distro])
+        dockerfile_path = "images/{}/Dockerfile".format(distro)
+        generate_dockerfile_directories(dockerfile_path)
+        with open(dockerfile_path, "w") as f:
+            f.write(dockerfile_content)

tools/circleci/images.yml

@@ -0,0 +1,2 @@
+trusty:
+  base_image: buildpack-deps:trusty-scm