How to fix git HEAD detached from a branch

$ git commit rear-release-notes.txt
# HEAD detached from rear-1.16

$ git branch
* (detached from rear-1.16)
  master

$ git checkout master
Warning: you are leaving 2 commits behind, not connected to
any of your branches:

  e9abc7a push release notes 1.16 (again)
  2f5d3fd adding the release notes for 1.16 to doc/

If you want to keep them by creating a new branch, this may be a good time
to do so with:

 git branch new_branch_name e9abc7a

Switched to branch 'master'

$ git branch temp e9abc7a
$ git checkout temp
Switched to branch 'temp'
$ git branch
  master
* temp
$ git log --graph --decorate --pretty=oneline --abbrev-commit master origin/master temp
* e9abc7a (HEAD, temp) push release notes 1.16 (again)
* 2f5d3fd adding the release notes for 1.16 to doc/
* 4581e52 (tag: rear-1.16, origin/master, origin/HEAD, master) prepare rear for new release 1.16
*   de337d4 Merge pull request #403 from ypid/df-encfs-fix

$ git diff master temp
diff --git a/doc/rear-release-notes.txt b/doc/rear-release-notes.txt
....

$ git diff origin/master temp
diff --git a/doc/rear-release-notes.txt b/doc/rear-release-notes.txt
....
$ git branch -f master temp
$ git checkout master
Switched to branch 'master'
Your branch is ahead of 'origin/master' by 2 commits.
  (use "git push" to publish your local commits)
$ git push
$ git branch -d temp
Deleted branch temp (was e9abc7a).