git：如何在创建分支之前获取master的最后一次提交

Question

I want to see the difference between a branch and the master immediately before the branch was created, to see all changes made to the branch.

I get my latest branch in a working directory (dirA/):

cd /home/me/dirA/
git clone <my remote repo>
git checkout my_branch

I want to then get the master just before I created my_branch: cd /home/me/dirB/ git clone How do I checkout the master commit immediately before I did my git branch my_branch before I changed my_branch ?

Answer 1

I want to see the difference between a branch and the master immediately before the branch was created, to see all changes made to the branch.

The ... operator can show all changes done in a branch compared to a base branch:

git diff origin/master...

(It's not a typo that there is nothing after the ... . This is equivalent to git diff origin/master...HEAD , just shorter to type.)

Answer 2

You've (probably inadvertently) asked two questions.

What you're trying to accomplish

I want to see the difference between a branch and the master immediately before the branch was created, to see all changes made to the branch.

is something for which git diff has special notation.

git diff master...my_branch

Note that ... is used somewhat differently by different commands. But for diff it does exactly what you want. (In particular, two dots does something different in the case of diff , which - if you're used to using .. with log , might be confusing.)

And while that's probably the information you really need, what you actually asked was

How do I checkout the master commit immediately before I did my git branch my_branch before I changed my_branch ?

To locate the commit you'd use

git merge-base master my_branch

In a bash shell, you could therefore say

git checkout `git merge-base master my_branch`

From your question, it seems you plan to check out each branch in a different clone. The only apparent advantage this has over using the git diff command above would be that both trees are on your file system, so if for some reason a tool you want to use for the comparison won't play nice with git, still you could use it.

Actually you could do that even without a second clone by using git worktree to check out a second working tree on a single repo; but that only really matters if either (1) there's substantial overhead to cloning (maybe because of dependency on an LFS store?), or (2) you plan to keep both working trees around and don't want to have to manage two databases / two sets of refs