Commit _subject_ filter, everywhere

[john at keeping.me.uk (John Keeping)]

On Wed, Nov 29, 2017 at 10:10:00PM +0100, Bjjjrn Forsman wrote:
> 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)?

I was going to suggest introducing a new subject-filter which is used to
filter the commit subject wherever it is displayed, but there is a
subtlety which makes this more complicated in the summary, log and refs
pages than it is in the commit page.

When we are showing a single-line summary of a commit, the subject is a
hyperlink so adding new content outside the existing subject is not
possible with the obvious filter implementation.

One option would be to push the <a></a> tag generation down into the
filter, but I'd rather avoid that if possible.

What do you think about adding a "filter" which is called before the
commit subject is printed and allows outputting additional HTML content?
("filter" is in quotes since there will not be any content copied
through the program.)