Use current "detached HEAD" message

Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/user-manual.txt

@@ -312,10 +312,17 @@ referenced by a tag:
 
 ------------------------------------------------
 $ git checkout v2.6.17
-Note: moving to "v2.6.17" which isn't a local branch
-If you want to create a new branch from this checkout, you may do so
-(now or later) by using -b with the checkout command again. Example:
-  git checkout -b <new_branch_name>
+Note: checking out 'v2.6.17'.
+
+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 427abfa... Linux v2.6.17
 ------------------------------------------------
 
@@ -326,7 +333,7 @@ and git branch shows that you are no longer on a branch:
 $ cat .git/HEAD
 427abfa28afedffadfca9dd8b067eb6d36bac53f
 $ git branch
-* (no branch)
+* (detached from v2.6.17)
   master
 ------------------------------------------------
 
@@ -3639,7 +3646,7 @@ working on a branch.
 
 -------------------------------------------------
 $ git branch
-* (no branch)
+* (detached from d266b98)
   master
 -------------------------------------------------