Add slim images (#140)

Add "slim" images for Ubuntu 16.04 and 18.04.  Slim images are images designed just for running an already built Swift program. Consequently, they do not contain the Swift compiler.

The normal and slim images can be combined via a multi-stage `Dockerfile` to produce a lighter-weight image ready for deployment.

Author: ianpartridge

5.0/ubuntu/16.04/slim/Dockerfile

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+FROM ubuntu:16.04
+LABEL maintainer="Swift Infrastructure <[email protected]>"
+LABEL Description="Docker Container for the Swift programming language"
+
+RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true && apt-get -q update && \
+    apt-get -q install -y \
+    libatomic1 \
+    libbsd0 \
+    libcurl3 \
+    libxml2 \
+    tzdata \
+    && rm -r /var/lib/apt/lists/*
+
+# Everything up to here should cache nicely between Swift versions, assuming dev dependencies change little
+ARG SWIFT_PLATFORM=ubuntu16.04
+ARG SWIFT_BRANCH=swift-5.0.1-release
+ARG SWIFT_VERSION=swift-5.0.1-RELEASE
+
+ENV SWIFT_PLATFORM=$SWIFT_PLATFORM \
+    SWIFT_BRANCH=$SWIFT_BRANCH \
+    SWIFT_VERSION=$SWIFT_VERSION
+
+# Download GPG keys, signature and Swift package, then unpack, cleanup and execute permissions for foundation libs
+RUN SWIFT_URL=https://swift.org/builds/$SWIFT_BRANCH/$(echo "$SWIFT_PLATFORM" | tr -d .)/$SWIFT_VERSION/$SWIFT_VERSION-$SWIFT_PLATFORM.tar.gz \
+    && apt-get update \
+    && apt-get install -y curl \
+    && curl -fSsL $SWIFT_URL -o swift.tar.gz \
+    && curl -fSsL $SWIFT_URL.sig -o swift.tar.gz.sig \
+    && export GNUPGHOME="$(mktemp -d)" \
+    && set -e; \
+        for key in \
+      # pub   4096R/ED3D1561 2019-03-22 [expires: 2021-03-21]
+      #       Key fingerprint = A62A E125 BBBF BB96 A6E0  42EC 925C C1CC ED3D 1561
+      # uid                  Swift 5.x Release Signing Key <[email protected]>
+          A62AE125BBBFBB96A6E042EC925CC1CCED3D1561 \
+        ; do \
+          gpg --quiet --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
+        done \
+    && gpg --batch --verify --quiet swift.tar.gz.sig swift.tar.gz \
+    && tar -xzf swift.tar.gz --directory / --strip-components=1 $SWIFT_VERSION-$SWIFT_PLATFORM/usr/lib/swift/linux \
+    && apt-get purge -y curl \
+    && apt-get -y autoremove \
+    && rm -r /var/lib/apt/lists/* \
+    && rm -r "$GNUPGHOME" swift.tar.gz.sig swift.tar.gz \
+    && chmod -R o+r /usr/lib/swift

5.0/ubuntu/18.04/slim/Dockerfile

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+FROM ubuntu:18.04
+LABEL maintainer="Swift Infrastructure <[email protected]>"
+LABEL Description="Docker Container for the Swift programming language"
+
+RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true && apt-get -q update && \
+    apt-get -q install -y \
+    libatomic1 \
+    libbsd0 \
+    libcurl4 \
+    libxml2 \
+    tzdata \
+    && rm -r /var/lib/apt/lists/*
+
+# Everything up to here should cache nicely between Swift versions, assuming dev dependencies change little
+ARG SWIFT_PLATFORM=ubuntu18.04
+ARG SWIFT_BRANCH=swift-5.0.1-release
+ARG SWIFT_VERSION=swift-5.0.1-RELEASE
+
+ENV SWIFT_PLATFORM=$SWIFT_PLATFORM \
+    SWIFT_BRANCH=$SWIFT_BRANCH \
+    SWIFT_VERSION=$SWIFT_VERSION
+
+# Download GPG keys, signature and Swift package, then unpack, cleanup and execute permissions for foundation libs
+RUN SWIFT_URL=https://swift.org/builds/$SWIFT_BRANCH/$(echo "$SWIFT_PLATFORM" | tr -d .)/$SWIFT_VERSION/$SWIFT_VERSION-$SWIFT_PLATFORM.tar.gz \
+    && apt-get update \
+    && apt-get install -y curl gpg \
+    && curl -fSsL $SWIFT_URL -o swift.tar.gz \
+    && curl -fSsL $SWIFT_URL.sig -o swift.tar.gz.sig \
+    && export GNUPGHOME="$(mktemp -d)" \
+    && set -e; \
+        for key in \
+      # pub   4096R/ED3D1561 2019-03-22 [expires: 2021-03-21]
+      #       Key fingerprint = A62A E125 BBBF BB96 A6E0  42EC 925C C1CC ED3D 1561
+      # uid                  Swift 5.x Release Signing Key <[email protected]>
+          A62AE125BBBFBB96A6E042EC925CC1CCED3D1561 \
+        ; do \
+          gpg --quiet --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
+        done \
+    && gpg --batch --verify --quiet swift.tar.gz.sig swift.tar.gz \
+    && tar -xzf swift.tar.gz --directory / --strip-components=1 $SWIFT_VERSION-$SWIFT_PLATFORM/usr/lib/swift/linux \
+    && apt-get purge -y curl gpg \
+    && apt-get -y autoremove \
+    && rm -r /var/lib/apt/lists/* \
+    && rm -r "$GNUPGHOME" swift.tar.gz.sig swift.tar.gz \
+    && chmod -R o+r /usr/lib/swift

Dockerfile.template

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+# swift-docker
+
+<img src="https://swift.org/assets/images/swift.svg" alt="Swift logo" height="70" >
+
+### An Ubuntu 16.04 and Ubuntu 18.04 Docker image for [Swift](https://swift.org).
+
+#### You can find the Docker Hub repo here: [https://hub.docker.com/_/swift/](https://hub.docker.com/_/swift/)
+
+
+### Usage
+
+##### Pull the Docker image from Docker Hub:
+
+```bash
+docker pull swift
+```
+
+##### Create a container from the image and run it:
+
+```bash
+docker run -it swift /bin/bash
+```
+
+If you want to run the Swift REPL you will need to run the container with additional privileges:
+
+```bash
+docker run --security-opt seccomp=unconfined -it swift
+```
+
+We also provide a "slim" image. Slim images are images designed just for running an already built Swift program. Consequently, they do not contain the Swift compiler.
+
+The normal and slim images can be combined via a multi-stage Dockerfile to produce a lighter-weight image ready for deployment. For example:
+
+```dockerfile
+FROM swift:latest as builder
+WORKDIR /root
+COPY . .
+RUN swift build -c release
+
+FROM swift:slim
+WORKDIR /root
+COPY --from=builder /root .
+CMD [".build/x86_64-unknown-linux/release/docker-test"]
+```
+
+## Contributions
+
+Contributions via pull requests are welcome and encouraged :)
+
+## License
+
+docker-swift is licensed under the [Apache License, Version 2.0](LICENSE.md).