CLI to get binaries from a docker image with multi arch support

have a look at the README.md to see how it works.

Bootstrap a CLI program to copy binaries from multi arch images

Signed-off-by: Gianluca Arbezzano <gianarb92@gmail.com>

README.md

@@ -16,3 +16,44 @@ that will may change a bit how Tinkerbell works.
 
 We are keeping the number of bc break as low as possible but in the current
 state they are expected.
+
+## Binary release
+
+As part of a new release for sandbox we want to push binaries to GitHub Release
+in this way the community will be able to use them if needed.
+
+We build Docker images across many architectures, each of them in its own
+repository: boots, hegel, tink and so on.
+
+Sandbox is just a collection of those services and we follow the same pattern
+for getting binaries as well.
+
+There is a go program available in `./cmd/getbinariesfromquay/main.go`. You can
+run it with `go run` or build it with `go build`:
+
+```terminal
+$ go run cmd/getbinariesfromquay/main.go -h
+  -binary-to-copy string
+        The location of the binary you want to copy from inside the image. (default "/usr/bin/hegel")
+  -image string
+        The image you want to download binaries from. It has to be a multi stage image. (default "docker://quay.io/tinkerbell/hegel")
+  -out string
+        The directory that will be used to store the release binaries (default "./out")
+  -program string
+        The name of the program you are extracing binaries for. (eg tink-worker, hegel, tink-server, tink, boots) (default "hegel")
+```
+
+By default it uses the image running on Quay for Hegel and it gets the binary
+`/usr/bin/hegel` from there. The directory `./out` is used to store images and
+binaries inside `./out/releases`.
+
+To get the binaries for example for boots you can run:
+
+```terminal
+$ go run cmd/getbinariesfromquay/main.go \
+    -binary-to-copy /usr/bin/boots \
+    -image docker://quay.io/tinkerbell/boots:sha-9625559b \
+    -program boots
+```
+
+You will find them in `./out/release`