Here is steps

1. Check out your own forked repository

git clone git@github.com:aidabo/Ghost.git

2. Link your local fork to the original repository to fetch updates:

git remote add upstream https://github.com/TryGhost/Ghost.git

3. Pull all branches, tags, and commits from the original repository:

git fetch upstream --tags

4. Create a branch based on the upstream tag (e.g., v5.116.2):

git checkout -b new-upstream-version v5.116.2

5. Rebase Your Custom Code onto the New Version

Rebase to apply your changes on top of the latest upstream code
(here git checkout custom-feature custom-feature is main, can be branch and tags):

   git checkout main
   git rebase new-upstream-version

Resolve conflicts during rebase, then continue:

   git rebase --continue

6. Resolve Merge/Rebase Conflicts

Git will pause if conflicts occur. Open conflicting files, edit them to resolve discrepancies, then mark them as resolved:

git add resolved-file.js

Complete the merge/rebase after resolving all conflicts and commit.

git commit -m "merged upgraded files"

7. Push Updated Code to Your Fork

git push origin main --force-with-lease