In issue #1815, it was reported that Gollum RSS feeds attempt to put
entire commit messages into a feed item's `<title>` element.
Given that commit messages can be many paragraphs long, this is not an
acceptable way to render a feed item title.
If a commit has many lines or paragraphs, we now put those inside the
`<description>` element as of this commit.
While I was editing this view, I decided it would be a good time to
increase test coverage, as this view renderer was not under test at
all. I also fixed a typo ("Commited" should say "Committed"). There are
implicit dependencies on other gems that provide the
`Gollum::Git::Commit`, `Gollum::Git::Actor`, and `Rugged::Commit`
classes here, so mocking out simple versions of their interfaces seemed
like the path of least resistance to setting up controllable tests.
I also removed some now-duplicated assertions from `test/test_app.rb`.
benjamin wil