digraph {
    node [shape = "box", style = "filled, rounded"]

    subgraph clusterorigin {
        label = "origin"

        node [color = orchid]

        omaster[label = "master"]
    }

    subgraph clusterlocal {
        label = "local"

        node [color = orchid]

        master[label = "master"]
    }

    subgraph clusteralice {
        label = "alice"

        node [color = limegreen]

        amaster[label = "master"]
    }

    subgraph clusterbob {
        label = "bob"

        node [color = lightskyblue]

        bmaster[label = "master"]
    }

    omaster -> master [label = "git pull"]
    master -> omaster [label = "git push", constraint = false]
    amaster -> master [label = "git pull alice", constraint = false]
    bmaster -> master [label = "git pull bob", constraint = false]
}