HEAD's reflog entry for a renamed branch

[Kyle Meyer]

Hello,

I noticed that, after renaming the current branch, the corresponding
message in .git/logs/HEAD is empty.

For example, running

    $ mkdir test-repo
    $ cd test-repo
    $ git init
    $ echo abc >file.txt
    $ git add file.txt
    $ git commit -m"Add file.txt"
    $ git branch -m master new-master

resulted in the following reflogs:

   $ cat .git/logs/refs/heads/new-master
   00000... 68730... Kyle Meyer <k...@kyleam.com> 1484607020 -0500      commit 
(initial): Add file.txt
   68730... 68730... Kyle Meyer <k...@kyleam.com> 1484607020 -0500      Branch: 
renamed refs/heads/master to refs/heads/new-master

   $ cat .git/logs/HEAD
   00000... 68730... Kyle Meyer <k...@kyleam.com> 1484607020 -0500      commit 
(initial): Add file.txt
   68730... 00000... Kyle Meyer <k...@kyleam.com> 1484607020 -0500

I expected the second line of .git/logs/HEAD to mirror the second line
of .git/logs/refs/heads/new-master.  Are the empty message and null sha1
in HEAD's entry intentional?

--
Kyle