anchor.diff:  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 "$key"; \
  -        done \
  -    && gpg --batch --verify --quiet swift.tar.gz.sig swift.tar.gz \
  +    && gpg --verify swift.tar.gz.sig \
       && tar -xzf swift.tar.gz --directory /usr/local --strip-components=2 \
       && rm -r "$GNUPGHOME" swift.tar.gz.sig swift.tar.gz
   
  
positive.code: 
  RUN mkdir /dependencies
  
  # Build libnghttp2
  ARG HTTP2_VERSION
  
  
negative.code:     make && \
      make install && \
      ldconfig
  
  # Install Swift
  ARG SWIFT_PLATFORM=ubuntu16.04
  ARG SWIFT_BRANCH
  