anchor.diff:  
   RUN mkdir /dependencies
   
  +# Install GPG keys
  +RUN wget -q -O - https://swift.org/keys/all-keys.asc | \
  +  gpg --import - \
  +  && export GNUPGHOME="$(mktemp -d)"
  +
   # Build libnghttp2
   ARG HTTP2_VERSION
   
  
positive.code: RUN SWIFT_URL=https://swift.org/builds/$SWIFT_BRANCH/$(echo "$SWIFT_PLATFORM" | tr -d .)/$SWIFT_VERSION/$SWIFT_VERSION-$SWIFT_PLATFORM.tar.gz \
      && curl -L $SWIFT_URL -o swift.tar.gz \
      && curl -L $SWIFT_URL.sig -o swift.tar.gz.sig \
      && export GNUPGHOME="$(mktemp -d)" \
      && set -e; \
          for key in \
              7463A81A4B2EEA1B551FFBCFD441C977412B37AD \
              1BE1E29A084CB305F397D62A9F597F4D21A56D5F \
              A3BAFD3556A59079C06894BD63BC1CFE91D306C6 \
          ; do \
              gpg --quiet --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
          done \
      && gpg --batch --verify --quiet swift.tar.gz.sig swift.tar.gz \
      && tar -xzf swift.tar.gz --directory /usr/local --strip-components=2 \
      && rm -r "$GNUPGHOME" swift.tar.gz.sig swift.tar.gz
  
  
negative.code:     make && \
      make install && \
      ldconfig
  
  # Install Swift
  ARG SWIFT_PLATFORM=ubuntu16.04
  ARG SWIFT_BRANCH
  