@bertwesarg Thanks for your contribution. May I ask why this is needed ? When creating refs using plain git, I don't see newlines either.
In case this is a bug you are fixing, you could add a test that goes green with this patch.
Thanks for the clarification.

Hmm, while I still use an ancient git 2.1.4 it does add a newline:

$ git init .$ hexdump -C .git/HEAD 00000000  72 65 66 3a 20 72 65 66  73 2f 68 65 61 64 73 2f  |ref: refs/heads/|00000010  6d 61 73 74 65 72 0a                              |master.|00000017

And git master should still do this:

https://github.com/git/git/blob/master/refs/files-backend.c#L2740

Though I noticed this because the git prompt provided by git-prompt.sh did not worked anymore, because it uses the shell read builtin, which does not work if the file does not has a trailing newline:

https://github.com/git/git/blob/master/contrib/completion/git-prompt.sh#L433

$ __git_ps1 '%s\n'master$ truncate -s 22 .git/HEAD$ __git_ps1 '%s\n'$

Thanks for the clarification and the thorough research, great to have this contribution merged now! I feel a bit silly that I was unable to 'see' the newline at the end of the symbolic ref with vim, but will certainly puthexdump on my map.