Cannot configure cgit to use custom notes refs

[Robie Basak]

git-ubuntu is using git-notes to publish the debian/changelog entry associated with individual synthesized commits, which we'd like to see appear in Launchpad's cgit view against those commits.

This works if we push to the default notes ref of refs/notes/commits, but this ref is likely to collide with users' possible own use of git-notes. It would be better for us to use a unique notes ref dedicated for this information. We've selected refs/notes/changelog for this purpose. However, cgit does not display notes under this ref by default, and Launchpad doesn't currently have any method to configure it.

As a workaround, I am having the importer push to "refs/notes/commits" and then have "git ubuntu clone" pull back to "refs/notes/changelog" on the client side.

To configure this in cgit, I believe that we need to set "notes.displayRef" (to refs/notes/changelog in this case, perhaps in addition to refs/notes/commits). Alternatively there's an environment variable that can be used. Colin suggested that Launchpad could grow a mechanism to set this on a per-branch basis similar to git_repository.default_branch.

Also see LP: #1633114 which discusses more rationale on the git-ubuntu side.

I don't currently see any urgency to fix this. It just leaves a wart on the importer fetch and push refspecs in the meantime.