We have a use case where one of our repositories is huge (multiple GB) with tens of thousands of remote branches. Doing a full `git fetch origin %s --prune +refs/heads/*:refs/heads/*` takes an unreasonable amount of time, and puts very high load on the servers.
We'd like to be able to specify the mask to be just `refs/heads/master:refs/heads/master` or some other glob.
This somewhat relates to the feature to 'import only' specific branches but is more focused on not fetching unused branches instead of not importing branches into the database.
We'd be okay with having this fully supplant the existing `import only` option (though I can't speak for other use cases).
At the moment we forked phabricator but this is not a great long term solution.