improve install from source

* Idempotent clone_and_build.sh does everything
* Add documentation for how to build in Docker

Had to sacrificy go generate because stringer apparently can't handle
vendor directory used by go dep, fails with error
on go generate rpc/frame_layer.go

refs #37

docs/installation.rst

@@ -38,22 +38,40 @@ The following list may be incomplete, feel free to submit a PR with an update:
 Compile From Source
 ~~~~~~~~~~~~~~~~~~~
 
-Check out the sources yourself, fetch dependencies using ``dep``, compile and install to the zrepl user's ``$PATH``.
-You may want to switch to a tagged commit (we use `semver <http://semver.org>`_) although a checkout of ``master`` branch should generally work.
-**Note**: if the zrepl binary is not in ``$PATH``, the examples in the :ref:`tutorial` may need to be adjusted.
+Go 1.9 or newer and a configured ``$GOPATH`` environment variable and a few build dependencies are required to build zrepl.
+A tutorial is available over at `golang.org <https://golang.org/doc/install>`_.
+If Go 1.9 is not available on your distro consider build in Docker (see below).
+
+The following shell script checks out the zrepl project into your ``$GOPATH``,
+installs the build dependencies, installs dependencies using ``dep ensure`` and does a ``make release``.
+Build artifacts are placed into ``$GOPATH/github.com/zrepl/zrepl/artifacts/``.
+
+When doing builds afterwards, it should be sufficient to checkout the new revision, run ``dep ensure`` and ``make release``.
+You may want to switch to a tagged commit (we use `semver <http://semver.org>`_) but master should generally be considered stable.
+
+**Note**: it is your job to install the apropriate binary in the zrepl users's ``$PATH``, e.g. ``/usr/local/bin/zrepl``.
+Otherwise, the examples in the :ref:`tutorial` may need to be adjusted.
+
+**You are encouraged to understand what happens by auditing the script.**
+
+::
+
+    curl 'https://raw.githubusercontent.com/zrepl/zrepl/master/clone_and_build.sh' | sh
+
+You can also build in a Docker container if you want an isolated build environment or don't have a compatible Go version.
 
 ::
 
-    # NOTE: you may want to checkout & build as an unprivileged user
-    cd /root
     git clone https://github.com/zrepl/zrepl.git
     cd zrepl
-    dep ensure
-    go build -o zrepl
-    cp zrepl /usr/local/bin/zrepl
-    rehash
-    # see if it worked
-    zrepl help
+    sudo docker run -it --rm \
+        -v "${PWD}:/zrepl" \
+        --user "$(id -u):$(id -g)" \
+        golang:latest bash -c 'export CLONEPATH=/go/src/github.com/zrepl; mkdir -p "$CLONEPATH" && ln -s /zrepl $CLONEPATH/zrepl && ${CLONEPATH}/zrepl/clone_and_build.sh'
+
+.. literalinclude:: ../clone_and_build.sh
+    :language: sh
+
 
 .. _mainconfigfile: