Use build/step-metadata

[flosell]

The next lambdacd-release (0.13.0) will contain support for build-metadata (flosell/lambdacd#138).
This could be used to make git-information more visible (e.g. to display the commit message that's being built prominently in the UI).

[flosell]

Two approaches are possible:

• Set git-information on build-metadata:
  • Useful for most pipelines, could just work out of the box.
  • Drawback: Could produce unpredictable results if pipeline contains more than one git-step. Could be resolved by adding a flag to disable setting metadata (in this case users would need the handle this themselves)
• Set git-information on step-metadata (not implemented in LambdaCD yet, see Introduce a concept of step-metadata lambdacd#86):
  • More fine-grained, does support multiple git steps out of the box
  • Would need extra work in UI, finding the right git-information to display for a step

tbd: Do we set metadata on clone or on successful wait-for?