A chat history between me and Copilot AI model to find out how to merge from the specific upstream main commit with the rest to the origin or local branch

upstream-main-cherry-pick.md

mmikhan: I fetched the upstream branch first, git fetch upstream and then merged, git merge upstream/main --allow-unrelated-histories. It had some conflicts that I resolved and merged eventually but that brought all the upstream commit history. all I wanted was the last commit instead of pulling the entire upstream commit history. how could have I done better?

GitHub Copilot: You're right! Merging with --allow-unrelated-histories pulled in the entire upstream commit history, which is often not what you want. Here are better approaches:

Option 1: Cherry-pick the specific commit

git fetch upstream
git cherry-pick <commit-hash>

This applies only the specific commit you want without bringing the entire history.

Option 2: Create a patch and apply it

git fetch upstream
git format-patch -1 upstream/main --stdout > upstream-changes.patch
git apply upstream-changes.patch
git add .
git commit -m "Apply upstream changes: [description]"

Option 3: Manual diff and apply

git fetch upstream
git diff HEAD upstream/main > changes.diff
# Review the diff, then apply manually or:
git apply changes.diff
git add .
git commit -m "Integrate upstream changes: [description]"

To fix your current situation:

You can clean up the history by doing an interactive rebase to squash the upstream commits:

git rebase -i HEAD~[number-of-commits-to-squash]

For future reference:

• Use git log --oneline upstream/main first to see what commits you're about to merge
• If you only want specific changes, cherry-pick individual commits
• If the repositories have completely different histories, consider whether you really need to merge or if copying specific files/changes manually might be cleaner

The cherry-pick approach would have been perfect for your use case!

mmikhan: while I want to cherry pick one, I want to get all the changes from the selected cherry pick to the rest of the recent but not all the old ones before from the cherry picked

GitHub Copilot: You want to cherry-pick a range of commits from a specific commit to the latest, not just one commit. Here's how to do that:

Option 1: Cherry-pick a range of commits

# Cherry-pick from a specific commit hash to the latest
git cherry-pick <starting-commit-hash>..upstream/main

Option 2: Find the commit you want to start from

# First, see the commit history to identify where you want to start
git log --oneline upstream/main

# Then cherry-pick from that point forward
git cherry-pick <commit-where-you-want-to-start>^..upstream/main

The ^ symbol means "starting from the commit before this one" so it includes your selected commit.

Option 3: Interactive cherry-pick (more control)

# Get the commit hashes you want
git log --oneline upstream/main | head -10

# Cherry-pick them one by one or in ranges
git cherry-pick <hash1> <hash2> <hash3>
# or
git cherry-pick <hash1>..<hash3>

To clean up your current situation:

Since you already merged everything, you can:

1. Reset to before the merge:

git reset --hard HEAD~1  # Go back one commit (before merge)

2. Then do the selective cherry-pick:

git cherry-pick <starting-commit>..upstream/main

This way you'll get only the commits from your chosen starting point to the latest, without all the old history.