git在3种方式合并后删除分支。 图表看起来像什么？

Question

I've been following Scott Chacon's Pro Git Book and I'm reaching the end of chapter 3 in which we have just done a three way merge. See the diagram below (my own drawn diagram not a screen grab of the book):

After doing the merge of ' master ' with ' issue53 ', resulting in merge commit c6 , the author says we can delete branch ' issue53 '.

git branch -d issue53

What actually happens to that branch under the hood and what would the resultant diagram look like? I ask this because the author does not address the issue. Would the branch still be there but just not pointed to? or is there some magic going on that I'm unaware of?

Answer 1

What actually happens to that branch under the hood

That depends on what you mean by the word branch . See What exactly do we mean by "branch"?

and what would the resultant diagram look like?

Drawing it in ASCII rather than fancy graphics, I get:

C0<-C1<-C2<-C4<---C6   <-- master (HEAD)
          \      /
           C3<-C5

That is, nothing happens to the commits at all. The name issue53 , however, which used to point to commit C5 , no longer exists (at all).

Since every commit in the diagram is still find-able by starting from the name master and working backwards, every commit remains protected from Git's garbage collection process.

Answer 2

A branch in git is just a pointer to a commit, and it has a very simple implementation - it is a text file containing the checksum of a commit it is pointing to.

So in this example, you would have a file .git/refs/heads/issue53 that represents your branch (is your branch).

And when you delete a branch in git, you delete that text file (pointer) representing that branch. In this case, .git/refs/heads/issu53