ci: more fixes for ci/kokoro/readme (#95)

These are some final tweaks:

* Add the "automatically generated warnings"
* Refactor the `FROM devtools AS readme` line
* Place `ARG NCPU=...` in the right places

Author: coryan

ci/kokoro/readme/Dockerfile.centos-7

@@ -12,19 +12,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=7
 FROM centos:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
-
-# Please keep the formatting in these commands, it is optimized to cut & paste
-# into the README.md file.
 
 ## [START README.md]
 
-# First install the development tools and OpenSSL.
-# The development tools distributed with CentOS (notably CMake) are too old to
-# build `google-cloud-cpp-common`. In these instructions, we use `cmake3`
-# obtained from [Software Collections](https://www.softwarecollections.org/).
+# Install the development tools and OpenSSL. The development tools distributed
+# with CentOS (notably CMake) are too old to build the
+# `google-cloud-cpp-common` project. We recommend you install cmake3 from
+# [Software Collections](https://www.softwarecollections.org/).
 
 # ```bash
 RUN rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
@@ -36,18 +38,13 @@ RUN yum makecache && \
 RUN ln -sf /usr/bin/cmake3 /usr/bin/cmake && ln -sf /usr/bin/ctest3 /usr/bin/ctest
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common
-# when using the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.centos-8

@@ -12,12 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=8
 FROM centos:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
-
-# Please keep the formatting in these commands, it is optimized to cut & paste
-# into the README.md file.
 
 ## [START README.md]
 
@@ -29,18 +31,13 @@ RUN dnf makecache && \
         zlib-devel
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.debian-buster

@@ -12,12 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=buster
 FROM debian:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
-
-# Please keep the formatting in these commands, it is optimized to cut & paste
-# into the README.md file.
 
 ## [START README.md]
 
@@ -30,18 +32,13 @@ RUN apt update && \
         pkg-config tar wget zlib1g-dev
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.debian-stretch

@@ -12,12 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=stretch
 FROM debian:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
-
-# Please keep the formatting in these commands, it is optimized to cut & paste
-# into the README.md file.
 
 ## [START README.md]
 
@@ -30,18 +32,13 @@ RUN apt update && \
         pkg-config tar wget zlib1g-dev
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.fedora

@@ -12,13 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=30
 FROM fedora:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
-
-# Please keep the formatting below, it is used by `extract-readme.sh` and
-# `extract-install.md` to generate the contents of the top-level README.md and
-# INSTALL.md files.
 
 ## [START README.md]
 
@@ -30,18 +31,13 @@ RUN dnf makecache && \
         zlib-devel
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.opensuse-leap

@@ -12,9 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=latest
 FROM opensuse/leap:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
 
 ## [START README.md]
 
@@ -26,18 +31,13 @@ RUN zypper refresh && \
         libcurl-devel libopenssl-devel make tar wget
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.opensuse-tumbleweed

@@ -12,9 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=latest
 FROM opensuse/tumbleweed:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
 
 ## [START README.md]
 
@@ -26,18 +31,13 @@ RUN zypper refresh && \
         libcurl-devel libopenssl-devel make tar wget zlib-devel
 # ```
 
-FROM devtools AS README
+## [END README.md]
+
+FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.ubuntu-bionic

@@ -12,12 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=bionic
 FROM ubuntu:${DISTRO_VERSION} AS devtools
-ARG NCPU=4
-
-# Please keep the formatting in these commands, it is optimized to cut & paste
-# into the README.md file.
 
 ## [START README.md]
 
@@ -30,18 +32,13 @@ RUN apt update && \
         pkg-config tar wget zlib1g-dev
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}

ci/kokoro/readme/Dockerfile.ubuntu-trusty

@@ -12,14 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+#
+# WARNING: This is an automatically generated file. Consider changing the
+#     sources instead. You can find the source templates and scripts at:
+#         https://github.com/googleapis/google-cloud-cpp-common/ci/templates
+#
+
 ARG DISTRO_VERSION=trusty
 FROM ubuntu:${DISTRO_VERSION} AS devtools
 ARG NCPU=4
 
-# Please keep the formatting below, it is used by `extract-readme.sh` and
-# `extract-install.md` to generate the contents of the top-level README.md and
-# INSTALL.md files.
-
 ## [START README.md]
 
 # Install the minimal development tools.
@@ -62,18 +64,13 @@ ENV OPENSSL_ROOT_DIR=/usr/local/ssl
 ENV PKG_CONFIG_PATH=/usr/local/ssl/lib/pkgconfig
 # ```
 
+## [END README.md]
+
 FROM devtools AS readme
 ARG NCPU=4
 
-## [START IGNORED]
-# Verify that the tools above are enough to compile google-cloud-cpp-common when using
-# the super build.
 WORKDIR /home/build/super
 COPY . /home/build/super
 RUN cmake -Hsuper -Bcmake-out \
         -DGOOGLE_CLOUD_CPP_EXTERNAL_PREFIX=$HOME/local
-RUN cmake --build cmake-out -- -j ${NCPU}
-# The tests will already be run as part of the build, no need to run it again.
-## [END IGNORED]
-
-## [END README.md]
+RUN cmake --build cmake-out -- -j ${NCPU:-4}