tree.dot

digraph tree {
    subgraph cluster_master {
        label="master"
        A1 -> A2 -> A3 -> A4 -> A4_B2_merge -> A5
        
        C1_new [label="C1"]
        C2_new [label="C2"]
        C1_new -> C2_new -> C3
        
//         br_master [shape=rectangle; label="master"]
        
    //     br_master -> A1 [style=dashed]
    //     br_master -> A2 [style=dashed]
         br_master -> C3
//         
         {rank=same; C3; br_master}
    }
    
    subgraph cluster_branching {
        label="branching"
        B1 -> B2
//         br_branching [shape=rectangle; label="branching"]
//         br_branching -> B2
//         {rank=same; B2; br_branching}
    }
    
    A3 -> B1
    B2 -> A4_B2_merge
    
    subgraph cluster_rebase {
        label="rebase"
        C1 [style=dashed]
        C2 [style=dashed]
        C1 -> C2
        br_rebase[label="rebase"; shape="rectangle"]
    }
    
    A4_B2_merge -> C1
    A5 -> C1_new
    br_rebase -> C3
    
    subgraph cluster_branching2 {
        label="branching2"
        D1 -> D2 -> D2_C3_merge
    }
    
    A4 -> D1
    C3 -> D2_C3_merge
}