Git detached head

Create a detached head situation

$ git branch
* master
$ git log --oneline
55fff69 v3
1fd2aa6 file1
$ git checkout 1fd2aa6
Note: checking out '1fd2aa6'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

HEAD is now at 1fd2aa6... file1
$ git log --oneline
1fd2aa6 file1
$ git log --oneline master
55fff69 v3
1fd2aa6 file1

Note:

1. git log shows only one entry (after detached head) as HEAD points to first commit.
2. git log master shows two entries as master points to 2nd commit.