旧版GitHub Desktop分支更新功能的Git命令行替代方案及原理咨询

Hey, I totally get missing that old GitHub Desktop button—it was super handy for quick merges with a dedicated commit! Let's break down exactly what it did and how to replicate it with Git commands, using your example scenario.

Core Git Command to Use #

The key command is straightforward, but you need to make sure you're on the right branch first. The old button's core action is equivalent to:

# Make sure you're on your target branch (the one you want to update)
git switch your-sub-branch
# Merge the source branch (e.g., master) into it
git merge master

Exact Logic of the Old GitHub Desktop Button #

Behind the scenes, the app was doing these steps automatically for you:

• Validate branch state: Confirmed you had the target branch (your sub-branch) checked out.
• Sync source branch: If your local copy of the source branch (e.g., master) was out of sync with the remote, it would quietly pull the latest commits first.
• Execute merge: Ran git merge <source-branch>. Since your sub-branch had new commits (D) that the source branch didn't, Git couldn't do a "fast-forward" merge—it had to create a new merge commit (G) that ties both branches' histories together.
• Handle commit message: Auto-filled a default merge commit message (like "Merge branch 'master' into your-sub-branch") and saved it for you.

Note: If you were merging a source branch where a fast-forward was possible (no new commits on your sub-branch), the old button actually used git merge --no-ff <source-branch> to force a merge commit, instead of just moving the branch pointer. That's a small but important detail if you ever run into that scenario.

Step-by-Step Walkthrough of Your Example #

Let's map this to your specific commit history:

• master: A → B → C → E → F
• sub-branch: A → B → C → D

Here's how to create merge commit G:

1. Switch to your sub-branch:

   # Use checkout if you're on an older Git version
   git checkout sub-branch
   # Or switch (newer Git versions)
   git switch sub-branch
   

2. Ensure master is up-to-date (skip this if all commits are local):

   git switch master
   git pull
   git switch sub-branch
   # Alternatively, fetch without switching branches:
   # git fetch origin master
   

3. Run the merge command:

   git merge master
   

   Git will open your default text editor with a pre-filled commit message (you can edit it if you want). Save and close the editor, and Git will create the merge commit G.

Your sub-branch's history will now look like:
A → B → C → D → G
Where G has two parent commits: D (the last commit on your sub-branch) and F (the last commit on master).

内容的提问来源于stack exchange，提问作者Ant