[bug in next ?] git-fetch/git-push issue

With the current tip of next[0], I have this bizare issue:

  * I have two branches say master, and next, I'm on next.

  * my master lags behind origin/master, but next is a fast-forward wrt
    origin/next.

Now I git push:

    ┌─(18:16)──<~/some/repo next>──
    └[artemis] git push
    error: remote 'refs/heads/master' is not an ancestor of
     local  'refs/heads/master'.
     Maybe you are not up-to-date and need to pull first?
    updating 'refs/heads/next'
      from xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
      to   yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
    Counting objects: 24, done.
    Compressing objects: 100% (14/14), done.
    Writing objects: 100% (14/14), done.
    Total 14 (delta 12), reused 0 (delta 0)
    refs/heads/next: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -> yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
    updating local tracking ref 'refs/remotes/origin/master'
    updating local tracking ref 'refs/remotes/origin/next'

And then I fetch, and here happens something really awkward:

    ┌─(18:17)──<~/some/repo next>──
    └[artemis] git fetch
    From ssh://some.host/some/repo.git
     * [new branch]      master -> origin/master

I believe there is something rotten in the kingdom of Denmark… though my heads seems to always be OK, I think it's just an output issue.

The fun part is that if next has nothing to push, nothing happens:

    ┌─(18:55)──<~/dev/mmsx next>──
    └[artemis] git push
    error: remote 'refs/heads/master' is not an ancestor of
     local  'refs/heads/master'.
     Maybe you are not up-to-date and need to pull first?
    error: failed to push to 'ssh://some.host/some/repo.git'
    ┌─(18:55)──<~/dev/mmsx next>──
    └[artemis] git fetch && echo $?
    0

  [0] actually it's a bit farther than the current next, but for
      parseopt thingies that are irrelevant here. My current origin/next
      is 76374a65c41b80fa83f27b4dd924bd3967a07d69