Git Pull未生成合并提交原因及过多合并提交危害

Your test steps failed to create divergent histories between the local and remote branches—this divergence is a prerequisite for Git to generate a merge commit during git pull. Here's the breakdown:

• After initializing test2, your local master branch had no commits (it was an empty repository).
• When you ran git pull origin master, Git fetched the remote master branch (with one commit) and performed a fast-forward merge: it simply moved your local master pointer to match the remote's commit, since there was no conflicting history to merge. This is why no merge commit appeared in gitk (note: your local branch should have the fetched commit—double-check if you had the correct branch checked out).

To reproduce the textbook scenario and trigger a merge commit, follow these adjusted steps:

1. Complete your original steps 1-4 (push the initial commit to GitHub).
2. In test2:
   • Run git init test2, git remote add origin [DUMMY_REPO_LINK], then git pull origin master to get the initial commit.
   • Create a new file, commit it locally (git add ., git commit -m "Local commit in test2").
3. Return to the original test repo:
   • Create another new file, commit it, then push to GitHub (git push origin master).
4. In test2, run git pull origin master.

Now your local test2 branch has a commit the remote lacks, and the remote has a commit your local branch doesn’t—their histories have diverged. Git will create a merge commit to combine the two histories, which you’ll see in gitk.

Excessive merge commits can harm your repository’s history and workflow in these key ways:

• Cluttered history: Merge commits add noise to the commit log, making it harder to trace the actual sequence of code changes. Most merge commits don’t contain meaningful updates—they only mark a point where branches were combined.
• Debugging complications: Tools like git bisect (used to find bug-introducing commits) become less efficient. You may need to skip merge commits or resolve unnecessary conflicts, slowing down debugging.
• Obscured context: A clean, linear history makes it easy to understand why changes were made. Merge commits break this linearity, forcing developers to jump between branches to follow the code’s evolution.
• Conflict resolution overhead: Frequent merges can lead to repeated conflict resolution, especially if branches stay out of sync for long periods. This wastes time and increases the risk of subtle bugs from poorly resolved conflicts.

内容的提问来源于stack exchange，提问作者Issac Howard