Git: How to return from 'detached HEAD' state

Use git reflog to find the hashes of previously checked out commits.

A shortcut command to get to your last checked out branch (not sure if this work correctly with detached HEAD and intermediate commits though) is git checkout -

If you remember which branch was checked out before (e.g. master) you could simply

git checkout master

to get out of detached HEAD state.

Generally speaking: git checkout <branchname> will get you out of that.

If you don't remember the last branch name, try

git checkout -

This also tries to check out your last checked out branch.