static should not fallback to master branch

[kptdobe]

See https://github.com/adobe/helix-static/blob/master/src/static.js#L75

Required for adobe/helix-pages#531: ref might be undetermined when requesting helix-static (default branch must be used). helix-static must then:

• allow ref parameter to be omitted
• if this is the case, determine the ref (default branch) - should be responsibility of adobe/helix-resolve-git-ref. See Default branch fallback fails helix-resolve-git-ref#287.

Requires adobe/helix-resolve-git-ref/issues/299 for simplicity of the change.

[trieloff]

Static is never called directly, so this is probably not a blocker

[kptdobe]

I think I (almost) agree. I am currently writing tests for the various overrides we may have...
I still found those direct requests to static:

• https://github.com/adobe/helix-publish/blob/master/layouts/fastly/helix.vcl#L535
• https://github.com/adobe/helix-publish/blob/master/layouts/fastly/helix.vcl#L590
  The ref is specified, I want to make sure the ref is correct in all combo.