We have a large git repo with lots of history and lots of branches. As of JENKINS-31393, we can now specify a refspec and have the initial fetch respect it.

We have two jobs for each repo. One that builds master, and one that builds everything except master. Specifying a refspec works for our master job, but won't for the feature branches job since it needs to be able to fetch more than just the specified refspec.

However, a shallow clone of all branches is too expensive and takes about 18 minutes to complete from inside the datacenter that contains our git repo.

It seems like the ideal is for the master to have a full clone of our repo to be able to do polling and figure out what branch / revision to build, and then for it to tell a slave what revision to do a shallow checkout using a full refspec so it only checks out that one branch.