DAG 与使用 Git 的树？
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DAG vs. tree using Git?
提问by Jonathan.Brink
I've often read that Git uses the directed acyclic graph(DAG) data structure, with each commit as a node, and things like branches and tags as pointers to nodes.
我经常读到 Git 使用有向无环图(DAG) 数据结构，将每个提交作为一个节点，将分支和标签等内容作为指向节点的指针。
But when I try to visualize my commit history using tools like gitk, it looks more like a tree than a graph since every parent-child relationship is directed one way.
但是当我尝试使用 gitk 之类的工具可视化我的提交历史时，它看起来更像是一棵树而不是图形，因为每个父子关系都是以一种方式指向的。
So, what's the difference between a DAG and a tree, specifically with regards to Git?
那么，DAG 和树之间有什么区别，特别是在 Git 方面？
回答by John Kugelman
But when I try to visualize my commit history using tools like gitk, it looks more like a tree than a graph since every parent-child relationship is directed one way.
但是当我尝试使用 gitk 之类的工具可视化我的提交历史时，它看起来更像是一棵树而不是图形，因为每个父子关系都是以一种方式指向的。
A DAG, like a tree, can be laid out such that all parent-child relationships are one-way. The difference between them is that nodes in a DAG can have multiple parents. The most common case of this in Git is when you do a merge. A merge commit will have all of the commits that were merged as parents. A tree doesn't allow nodes to have multiple parents.
一个 DAG，就像一棵树，可以布置成所有的父子关系都是单向的。它们之间的区别在于 DAG 中的节点可以有多个父节点。Git 中最常见的情况是进行合并时。合并提交将具有作为父项合并的所有提交。一棵树不允许节点有多个父节点。
（图片来源）
Notice how the merge commit C6 has two parents, C4 and C5.
注意合并提交 C6 有两个父级 C4 和 C5。
