Add gget Docker image

Author: dpb587

README.md

@@ -50,6 +50,21 @@ Use `--help` to see all options and learn more about advanced usage.
 
     gget --help
 
+## Docker Usage
+
+The `dpb587/gget` image can be used as a build stage for finding and downloading assets for use in a subsequent stage.
+
+```
+FROM dpb587/gget as gget
+RUN gget --exec github.com/cloudfoundry/bosh-cli bosh=bosh-cli-*-linux-amd64
+RUN gget --exec github.com/cloudfoundry/bosh-bootloader bbl=bbl-*_linux_x86-64
+RUN gget --stdout github.com/pivotal-cf/om om-linux-*.tar.gz | tar -xzf- om
+
+FROM ubuntu
+COPY --from=gget /result/* /usr/local/bin/
+...everything else for your image...
+```
+
 ## Services
 
 The following services are supported through their APIs:

build/docker/gget/Dockerfile

@@ -0,0 +1,19 @@
+FROM alpine as base
+RUN apk add --no-cache ca-certificates wget
+
+ENV gget /usr/local/bin/gget
+RUN true \
+  && wget -qO "$gget" https://github.com/dpb587/gget/releases/download/v0.1.0/gget-0.1.0-linux-amd64 \
+  && echo "418b68caeb302898322465abc31c316a1dbdb7872cdad0fe4a9661c5118860c4  $gget" | sha256sum -c \
+  && chmod +x "$gget"
+RUN gget github.com/dpb587/gget --exec "$gget=gget-*-linux-amd64"
+RUN gget --version -v
+
+FROM alpine
+RUN apk add --no-cache ca-certificates xz
+COPY --from=base /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
+COPY --from=base /usr/local/bin/gget /bin/gget
+RUN mkdir /result
+WORKDIR /result
+ENTRYPOINT ["/bin/gget"]
+CMD ["--help"]