Commit _subject_ filter, everywhere

Hi Jason, all,

I got this idea to generate a link to the CI server job in front of
each commit message subject. Think small green/red boxes that are
clickable. I figure that getting the build status directly in cgit is
much more efficient than navigating the CI server itself, which
typically requires many clicks to find the build that comes out of a
given commit.

I had high hopes for the the commit-filter= setting, but found that

* commit-filter= is only run when showing a full commit, not other
places. I.e. it is applied when showing the "commit" tab, but not on
"summary", "logs" or "refs".
* commit-filter= is run twice on a commit message. Once for the
subject and once for the body. I expected only once. (Is this a bug?)

Any thoughts on if/how this use case can be supported? A separate
filter? Or simply run commit-filter= everywhere (breaking change)?

Best regards,
Bj?rn Forsman (happy cgit user)