Suppose the final paragraph of a commit message looks like this:
    """
    And here's the final paragraph.
    Bug: 1234
    TBR=soandso
    Change-Id: deadbeef
    """
In this case, we don't want to lose the Bug and Change-Id footers,
so we process the whole final paragraph. *But* we'd also like to
help the user get things formatted correctly. This change lets
git_footers notice this situation, and insert a newline before the
first well-formed footer (Bug: in this case), so that the set of
well- and mal-formed footers are separated from the rest of the
malformed body text.

In the rare case where the last line of the last non-trailer paragraph
is a url, this will also visibly push the url into the block of
trailers (where it doesn't belong), prompting the user to fix it.
A more comprehensive fix for that particular case is coming later.

Bug: 766234
Change-Id: I6ae0072fff68ddf06e6f43b70f9a82a7f247f4ab
Reviewed-on: https://chromium-review.googlesource.com/849481Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>