Default config.assets.digests to true in development

[namuorg]

With rails/sprockets-rails#149, assets will only be served if the request has a digest if config.assets.digest = true and config.assets.raise_runtime_errors = true.

This PR sets config.assets.digest to true by default and will help users avoid hardcoding paths that work in development but break in production.

[rafaelfranca]

Cool! Change the Gemfile to point to sprockets-rails master and we run the test suite against it.

[namuorg]

No longer results in false positives thanks to rails/sprockets-rails#84.

[namuorg]

Done!

[namuorg]

From a quick glance at the CI failures, it seems like there are instances in the tests that request assets without their digests and some asserts that expect the non-digested URL (e.g. expecting /src='\/\/example\.com\/assets\/rails\.png'/ when actual is "var src='//example.com/assets/rails-495b94d9cdd18b3a6eba96326cd909de.png';\n")

I'll take a look at turning off the digest flag when appropriate for some of the tests and amending the regex to include a digest for others.

[rafaelfranca]

Do we need to disable digest for this case?

[namuorg]

Yup, we need to disable it. We make a GET to "/assets/demo.js" which doesn't work when digests are enabled since a digest isn't included in the request URL.

[rafaelfranca]

Could you add a CHANGELOG entry?

[namuorg]

Sure. Do you mean another CHANGELOG entry in addition to the one already added to railties/CHANGELOG.md?

[rafaelfranca]

Oops, it is there already. thanks.

[namuorg]

Thanks @rafaelfranca and @matthewd for your help in getting this and rails/sprockets-rails#149 done!