State
-----
 -> * 3b1e4d8 F
    * fb2c608 E
    * cdd8ac5 D
    * aefe3ee C
    * 458bb4f B
    * 17fa95e A
currently "active" commit: F  (represented by ->)


Undo
----

    * 3b1e4d8 F
 -> * fb2c608 E
    * cdd8ac5 D
    * aefe3ee C
    * 458bb4f B
    * 17fa95e A

Note that F is still visible and not lost

Undo
----

    * 3b1e4d8 F
    * fb2c608 E
 -> * cdd8ac5 D
    * aefe3ee C
    * 458bb4f B
    * 17fa95e A

Redo
----

    * 3b1e4d8 F
 -> * fb2c608 E
    * cdd8ac5 D
    * aefe3ee C
    * 458bb4f B
    * 17fa95e A

Change G
----

 -> * f12ea02 G
    |  * 3b1e4d8 F
    | /
    * fb2c608 E
    * cdd8ac5 D
    * aefe3ee C
    * 458bb4f B
    * 17fa95e A

Note that the commit F is not lost from history/log