Update readme + scripts

Branch build-from-scratch in https://github.com/ochafik/bazel.git now compiles deps as needed

Dockerfile

@@ -1,7 +1,5 @@
 # See README.md
 FROM resin/rpi-raspbian:stretch
-ADD build_from_scratch.sh /
-
 RUN apt-get update
 
 # Needed for apt-key on the debian:stretch image.
@@ -20,4 +18,7 @@ RUN apt-get install -y automake g++ libtool make curl git python unzip wget zip
   apt-get autoremove && \
   apt-get clean
 
-RUN cd / && bash ./build_from_scratch.sh
+RUN cd / && \
+  git clone https://github.com/ochafik/bazel.git -b build-from-scratch --depth=1 && \
+  cd bazel && \
+  VERBOSE=yes bash ./compile.sh

README.md

@@ -15,8 +15,8 @@ Unfortunately, Raspbian doesn't have (yet) a package for Bazel. And Bazel
 doesn't provide (yet) a binary for armhf. And their instructions to build from
 source either implies you have a binary (which we don't) or that you battle with
 compilation errors. Which I did in
-[ochafik/bazel](https://github.com/ochafik/bazel/tree/from-scratch) (hopefully
-to be merged back into the original repo), and here I'm using it to build...
+[ochafik/bazel](https://github.com/ochafik/bazel/tree/build-from-scratch) (hopefully
+to be pulled back into the original repo), and here I'm using it to build...
 
 ## A Docker image to run Raspbian w/ Bazel on your Desktop
 
@@ -51,38 +51,30 @@ docker run --rm -ti ochafik/rpi-raspbian-bazel /bin/bash
 
 ## From sources on a Raspberry Pi
 
-Prerequisite: you'll need a large SD card, and the following packages (assumes
-you already have an Oracle JDK8 installed, as is the case on NOOBS distros,
-otherwise try `sudo apt-get install default-jdk`):
+Prerequisite: you'll need a large SD card, and the following packages:
 
 ```bash
 sudo apt-get update
 sudo apt-get install -y automake g++ libtool make curl git python unzip wget zip
+sudo apt-get install -y oracle-java8-installer oracle-java8-set-default
+
 # Reclaim as much space as we can: we'll need it.
 sudo apt-get autoremove
 sudo apt-get clean
 ```
 
-Now download my [script](./build_from_scratch.sh) and convince yourself it's safe:
-- It clones [ochafik/bazel](https://github.com/ochafik/bazel)
-  (my fork of [bazelbuild/bazel](https://github.com/bazelbuild/bazel))
-- Either your trust me, or you can fork my fork, check it doesn't contain dodgy
-  [diffs against the original repo](https://github.com/bazelbuild/bazel/compare/master...ochafik:from-scratch)
-  (assuming you trust the original, which I assume to be the case if you want to
-  use Bazel), edit the script to clone your fork instead (in case I sneakily
-  modified my fork after you scrutinized it), and proceed to the next command
+Clone [ochafik/bazel](https://github.com/ochafik/bazel) (my fork of
+[bazelbuild/bazel](https://github.com/bazelbuild/bazel)) and build it:
 
 ```bash
-wget https://raw.githubusercontent.com/ochafik/rpi-raspbian-bazel/master/build_from_scratch.sh
-# Do not trust scripts you download off the net!
-less build_from_scratch.sh
-
-bash build_from_scratch.sh
+git clone https://github.com/ochafik/bazel -b build-from-scratch --depth=1
+cd bazel
+bash ./compile.sh
 ```
 
 ## Building the Raspberry Pi Docker image:
 
-We aim to publish images every now and then, but you may rebuild the image at 
+I aim to publish images to docker hub soon, but you may rebuild the image at 
 any time with the following command (*takes a while*):
 
 ```bash
@@ -106,5 +98,6 @@ And if you want to test the `Dockerfile` itself faster on an image that does
 not require QEMU:
 
 ```bash
-docker build -t debian-bazel -f Dockerfile.debian .
+cat Dockerfile | sed 's/resin\/rpi-raspbian:stretch/debian:stretch/' > Dockerfile.debian
+docker build -t debian-bazel-build -f Dockerfile.debian .
 ```

build_debian_and_raspbian_docker_images.sh

@@ -1,30 +1,51 @@
 #!/bin/bash
 set -eux
 
-if [[ ! -d dist-amd64 ]]; then
-  cat Dockerfile | sed 's/resin\/rpi-raspbian:stretch/debian:stretch/' > Dockerfile.debian
-  docker build -t debian-bazel-build -f Dockerfile.debian .
-
-  mkdir dist-amd64
-  id=$(docker create debian-bazel-build)
-  docker cp $id:bazel/output/bazel dist-amd64
-  docker rm -v $id
-  echo "
-  FROM debian-bazel-build
-  COPY ./dist-amd64/bazel /usr/bin
-  " > Dockerfile.debian-slim
-  docker build -t debian-bazel -f Dockerfile.debian-slim .
-fi
-
-if [[ ! -d dist-armhf ]]; then
-  docker build -t rpi-raspbian-bazel-build .
-  mkdir dist-armhf
-  id=$(docker create rpi-raspbian-bazel-build)
-  docker cp $id:bazel/output/bazel dist-armhf
-  docker rm -v $id
-  echo "
-  FROM rpi-raspbian-bazel-build
-  COPY ./dist-armhf/bazel /usr/bin
-  " > Dockerfile.raspbian-slim
-  docker build -t rpi-raspbian-bazel -f Dockerfile.raspbian-slim .
-fi
+readonly BAZEL_OUTPUT=/bazel/output/bazel
+
+function build_bazel_docker() {
+  local build_image_base="$1"
+  local build_image_name="$2"
+  local normal_image_base="$3"
+  local normal_image_name="$4"
+  local slim_image_base="$5"
+  local slim_image_name="$6"
+  local dist_dir="$7"
+
+  if [[ ! -d "$dist_dir" ]]; then
+    cat Dockerfile | \
+      sed "s/resin\/rpi-raspbian:stretch/$(echo "$build_image_base" | sed 's/\//\\\//g')/" |
+      docker build -t "$build_image_name" -
+
+    mkdir -p "$dist_dir"
+    id=$(docker create "$build_image_name")
+    docker cp "$id:$BAZEL_OUTPUT" "$dist_dir"
+    docker rm -v $id
+
+    echo "
+      FROM $normal_image_base
+      COPY ./$dist_dir/bazel /usr/bin
+    " | \
+      docker build -t "$normal_image_name" -
+
+    echo "
+      FROM $slim_image_base
+      COPY ./$dist_dir/bazel /usr/bin
+    " | \
+      docker build -t "$slim_image_name" -
+  fi
+}
+
+# Use native Debian as a canary of sorts: this will fail way faster than the
+# QEMU rasbian build.
+build_bazel_docker \
+  debian:stretch      debian-bazel-build \
+  debian:stretch      debian-bazel \
+  debian:stretch-slim debian-bazel-slim \
+  dist-amd64
+
+build_bazel_docker \
+  resin/rpi-raspbian:stretch      rpi-raspbian-bazel-build \
+  resin/rpi-raspbian:stretch      rpi-raspbian-bazel \
+  resin/rpi-raspbian:stretch-slim rpi-raspbian-bazel-slim \
+  dist-armhf