Commits know their Parent
-------------------------

[graphviz]
----
digraph {
  node [shape=box, style=filled, fillcolor="#ABFFBB", fontname=arial, fontsize=18]

  L [label="", shape=box, width=0, height=0]
  R [label="", shape=box, width=0, height=0]
  {rank=source; L; R}
  commit1 [fillcolor="#FFAAA1", label="Commit 1"]
  commit2 [fillcolor="#FFAAA1", label="Commit 2"]
  commit3 [fillcolor="#FFAAA1", label="Commit 3"]

  snapshot1 [fillcolor=grey, label="Snapshot 1"]
  snapshot2 [fillcolor=grey, label="Snapshot 2"]
  snapshot3 [fillcolor=grey, label="Snapshot 3"]
  commit1 -> snapshot1
  commit2 -> snapshot2
  commit3 -> snapshot3

  commit1 -> commit2 -> commit3 [dir=back]
  {rank=same; commit1; commit2; commit3 }
  L -> commit1 [style=invis]
  R -> commit3 [style=invis]
  L -> R [label=time, arrowhead=normal, fontsize=20, fontname=arial]
}
----

[role="incremental"]
* each commit knows its parent