Move build steps into a shell script

[chrismytton]

Problem

We're trying to run multiple external commands in Ruby, which is awkward and means we have to perform lots of logic capturing output and checking exit statuses. This is an error-prone process and is basically trying to do something in Ruby which is trivial in shell script.

Proposed solution

Move the build steps, (obtaining and setting up the everypolitician-data repo, performing the build and pushing the result to a branch), into a shell script and then call that script from the RebuilderJob#perform method. This will reduce the amount of external commands we call and as a bonus means that any non-build errors, e.g. with bundle install, will get sent to Rollbar.

Related issues

• Prototype of moving build logic to shell script [WIP] Prototype of moving build logic to shell script #66

This should also help us fix the following issues:

• Create a lightweight ep-data mock repo for testing Create a lightweight ep-data mock repo for testing #44 - we can potentially just have a simpler script for local testing that doesn't do the full clone
• Handle all errors from external commands Handle all errors from external commands #52 - if we're only running one external command this becomes much easier.
• Speed up rebuilds by eliminating git clone and bundle install Speed up rebuilds #60 - having everything in one script makes it easier to experiment with shallow clones and the like
• Refactor RebuilderJob#perform method Refactor RebuilderJob#perform method #62 - this method should be simplified by moving the bulk of the build logic out.