Output HTML artifact containing all failures

[alekstorm]

Buildkite annotations, which this plugin creates, are limited to 100KB, and this plugin has a sophisticated algorithm for truncating the annotation to only the number of failures that would generate a Markdown-formatted annotation of less than that size. With stacktraces, that number can be as low as 15 failures: a small fraction of what a change to a large monorepo can cause.

This change causes the plugin to also upload an artifact containing the HTML-ified non-truncated Markdown output, and link to that artifact from the annotation if the annotation has been truncated.

This requires a refactor: Truncater now knows nothing about Formatter or Markdown; it only handles the truncation algorithm on the strings returned by a block. Much of the logic to wire Truncater and Formatters together has been moved to a new Processor class (this name was too similar to "Runner", so I renamed that to "Main"). This makes each class a bit more cohesive: Truncater only handles string truncation, Processor hands off the result of Formatter to Truncater, and Main writes the result of Processor to annotations and artifacts.

Also:

• I repurposed the test_layout template to also wrap the artifact, making the appearance similar to the annotation within Buildkite's UI.
• There's now a mixin for classes that want to reraise-or-log, depending on the result of a fail_on_error method, and any error can now be accompanied by a "diagnostics" JSON object.
• We now have a runtime dependency on a Markdown-to-HTML converter, so I switched to Kramdown, which is pure Ruby. The current minimal Dockerfile doesn't have the tools to compile C extensions.

[alekstorm]

Bump. Is there any update on this?

[maschwenk]

@liath want to take a look?