commandDependency.go

package main

import (
	"fmt"
	"strings"
)

func main() {
	t1 := NewNode("A")
	t2 := NewNode("B", t1)
	t3 := NewNode("C", t1)
	t4 := NewNode("D", t1, t2)
	t5 := NewNode("E", t3, t4)

	fmt.Println(t2)
	fmt.Println(t3)
	fmt.Println(t4)
	fmt.Println(t5)
}

type Node struct {
	Cmd       string
	DependsOn []*Node
}

func (n Node) String() string {
	deps := []string{}

	for _, d := range resolveDeps(&n) {
		deps = append(deps, d.Cmd)
	}

	return n.Cmd + ": " + strings.Join(deps, " -> ")
}

func NewNode(cmd string, deps ...*Node) *Node {
	return &Node{
		Cmd:       cmd,
		DependsOn: deps,
	}
}

func resolveDeps(roots ...*Node) []*Node {
	seen := map[*Node]bool{}
	all := []*Node{}

	var walk func(n *Node)

	walk = func(n *Node) {
		if seen[n] {
			return
		}
		seen[n] = true
		for _, n1 := range n.DependsOn {
			walk(n1)
		}
		all = append(all, n)
	}

	for _, r := range roots {
		walk(r)
	}
	return all
}

type executionPlan [][]*Node

func ExecutionPlan(nodes ...*Node) executionPlan {
	return nil
}

Live code - https://play.golang.org/p/YXnNhHl01G