+'git checkout' --detach [<branch>]::
+'git checkout' <commit>::
+
+ Prepare to work on top of <commit>, by detaching HEAD at it
+ (see "DETACHED HEAD" section), and updating the index and the
+ files in the working tree. Local modifications to the files
+ in the working tree are kept, so that the resulting working
+ tree will be the state recorded in the commit plus the local
+ modifications.
++
+Passing `--detach` forces this behavior in the case of a <branch> (without
+the option, giving a branch name to the command would check out the branch,
+instead of detaching HEAD at it), or the current commit,
+if no <branch> is specified.
+