TLDR: Read comments #11 and #12.
Updating core code from 8.0.6 to 8.1.0 results in numerous merging conflicts when tracking drupal.org upstream.
Example:
git remote -v
origin git@git.xxxxxx:drupal/xxxx.git (fetch)
origin git@git.xxxxxx:drupal/xxxx.git (push)
upstream http://git.drupal.org/project/drupal.git (fetch)
upstream http://git.drupal.org/project/drupal.git (push)
git fetch
git merge 8.1.0
Notice the massive amount of merge conflicts that ensue.
Automatic updates to drupal projects are now failing.
The process of updating a code base by extracting a downloaded tar.gz or zip, and reapplying changes manually in a development settings is far from best practice.
This is what version control is for.
The update procedure that professional teams have been using for years is as described here: https://www.drupal.org/node/803746#updatecore → however this no longer works.
The only way now to update the core code in a project is to extract a tarball over the projects code and then manually reapply any updates and patches. Which is infeasible in a professional development environment, with automated ci/cd systems and update processes. Automatic update processes fail as manual intervention is now required, and git history for the core code is lost.
CONFLICT (modify/delete): vendor/wikimedia/composer-merge-plugin/src/Merge/ExtraPackage.php deleted in 9.1.0 and modified in HEAD. Version HEAD of vendor/wikimedia/composer-merge-plugin/src/Merge/ExtraPackage.php left in tree.
Removing vendor/symfony/http-kernel/Exception/ConflictHttpException.php
CONFLICT (modify/delete): vendor/jcalderonzumba/mink-phantomjs-driver/composer.json deleted in 8.1.0 and modified in HEAD. Version HEAD of vendor/jcalderonzumba/mink-phantomjs-driver/composer.json left in tree.
CONFLICT (modify/delete): vendor/jcalderonzumba/gastonjs/src/Client/poltergeist.js deleted in 8.1.0 and modified in HEAD. Version HEAD of vendor/jcalderonzumba/gastonjs/src/Client/poltergeist.js left in tree.
...
CONFLICT (content): Merge conflict in core/assets/vendor/ckeditor/lang/eu.js
CONFLICT (content): Merge conflict in core/assets/vendor/ckeditor/ckeditor.js
CONFLICT (content): Merge conflict in core/assets/vendor/ckeditor/CHANGES.md
CONFLICT (content): Merge conflict in core/CHANGELOG.txt
CONFLICT (content): Merge conflict in .htaccess
Closed: outdated
Correction/Clarification
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.
The page in the issue summary is now deprecated and the question itself has been answered. The Git version control system → has evolved and has much more detail since this issue was opened.
I am going to close this as outdated. If anyone disagrees, re-open and explain what needs to be done.
In addition, merging upstream into a site project is not a recommended workflow for Drupal in 2025.