improved use of docker_tag

[ytjohn]

This change allows the components to use the actual base image you build during a make build. Resolves #26.

Also, added a "Starting build" line to the Makefile to make it easier to see determine which component is currently being built.

[arm4b]

Thanks for the PR!

Looks like just var rename would work for the child Dockerfiles?

[arm4b]

If we add new DOCKER_TAG into child Dockerfiles, looks like we don't need ST2_VERSION in them anymore and that would be just a var rename. Am I missing something?

-ARG ST2_VERSION
+ARG DOCKER_TAG
-FROM stackstorm/st2:${ST2_VERSION}
+FROM stackstorm/st2:${DOCKER_TAG}

[ytjohn]

st2web and st2chatops (and base, though that's out of scope) rely on ST2_VERSION in their build for running scripts and packages. The others could just be a variable rename, but it would require some additional logic in the Makefile.

RUN if [ "${ST2_VERSION#*dev}" != "${ST2_VERSION}" ]; then \
& apt-get install -y st2web=${ST2_VERSION}-* \
&& apt-get install -y st2chatops=${ST2_VERSION}-* \

[arm4b]

I see now, thanks!

So let's then rename var that won't require any additional Makefile changes?
st2 services like st2actionrunner, st2sensorcontainer... and so on.

So we won't have unused ST2_VERSION var in the Dockerfiles.

[ytjohn]

I'll revisit this later this week. I think it'll be a simple update, and it shouldn't hold up any other PRs for 3.3dev.