Add danger to start automating some code review tasks

[shilman]

Issue: N/A

What I did

• Testing out Danger http://danger.systems/js/guides/getting_started.html
• add a rule that requires labels for the pr-log that generates our CHANGELOG

How to test

Modify this PR and wait for messages from @storybookbot

[storybookbot]

	Fails
🚫	PR is not labeled with one of: ["cleanup","breaking","feature","bug","documentation","maintenance","greenkeeper","other"]

Generated by 🚫 dangerJS

[codecov]

Codecov Report

Merging #1251 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master    #1251    +/-   ##
========================================
  Coverage   13.73%   13.73%            
========================================
  Files         207      207            
  Lines        4638     4638            
  Branches      518      648   +130     
========================================
  Hits          637      637            
+ Misses       3545     3448    -97     
- Partials      456      553    +97

Impacted Files	Coverage Δ
app/react/src/client/preview/reducer.js	0% <0%> (ø)	⬆️
addons/storyshots/src/test-bodies.js	0% <0%> (ø)	⬆️
lib/ui/src/modules/api/configs/init_api.js	40.47% <0%> (ø)	⬆️
addons/knobs/src/components/types/Number.js	8.06% <0%> (ø)	⬆️
addons/knobs/src/components/types/Boolean.js	11.62% <0%> (ø)	⬆️
lib/ui/src/modules/shortcuts/actions/shortcuts.js	6.25% <0%> (ø)	⬆️
lib/ui/src/libs/key_events.js	23.25% <0%> (ø)	⬆️
.../ui/src/modules/ui/components/layout/dimensions.js	15.62% <0%> (ø)	⬆️
lib/ui/src/modules/ui/containers/left_panel.js	20% <0%> (ø)	⬆️
app/react/src/client/preview/init.js	0% <0%> (ø)	⬆️
... and 24 more

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[orta]

This makes sense, but only if you consider that an org contributor can set labels - so an OSS contribution wouldn't be able to do this - so it might be worth changing it to warn ( or to check whether the PR author is in the storybooks org )

[ndelangen]

https://travis-ci.org/storybooks/storybook/builds/241739179#L1335

The command "npm run danger" exited with 1.

[ndelangen]

I don't think the CI should fail on this? Shouldn't danger have it's own status?

[orta]

This run was specifically set to fail if specific labels were missed - so an exit code of 1 is OK, I think you can give Danger access to set a CI status independently of write access to a repo, which should make it show as one of the checks above

[shilman]

@orta I agree with @ndelangen that it should just show up as a failing check like any of the other services above (e.g. codefactor, codecov, etc.)

I have just expanded the token access to commit status now, but danger still exits with a code of 1, breaking the travis build. Should this work?

[orta]

I think so, I know the ruby version does this - unsure if the JS version does

[shilman]

@orta Looks like it does not, so I filed this issue: danger/danger-js#279

I'll try to take a whack at it at some point. In the meantime, I've converted it to a warning so that it does not break the build.