AFAIK, we can't make HEAD detached in an empty Git repository, so we need
to temporarily switch to the new default branch before checking out.
Fixes#2047
They are shown next to the change and commit id, since they are other names the
commit can be referred by.
The description is separated from the branches by a ` | ` when there are
branches, so that one can tell the branches from the description without color.
The result looks like this: 
