Collaborative Git (PartII)

In this part, you will learn basically how to handle conflicts.

Conflict or not ?

Let’s imagine you have added some new functionalities to your preprocessing code (branch preprocess_test):

$ echo "one-hot encoding" >> preprocessing_test.py

Add it to the index and commit it.

While you have added this preprocess, your colleague has focused on a new method to optimize the model:

$ cd ../colleague_computer
$ git checkout -b new_opti__model

He/she changes the script as follows:

$ echo "new opti method: 90% Accuracy" >> first_model.py
$ git commit -am "new opti method"
$ git push

This creates a PR and you accept the merge pull request.

After that, you continue your work on preprocessing:

$ cd ../mycomputer
$ echo "improve encoding" >> preprocessing_test.py
$ git commit -am "improve encoding"
$ git push

But you do not have the last code of your colleague (you do not have pull the main branch) and you may think that you overwrite his/her file. This is wrong since you require Git to merge the “commits”: you have not modified/committed the file “first_model.py”. So you can create a PR and merge it. In this situation, no conflict exists. Let’s explore a conflictual situation where you and your colleague modify the same file.

Real Conflict

You come the morning to work and retrieve the last modifications on the main branch (as well as your colleague). Create a new branch and modify “first_model.py”. During this time, your colleague modify the file “first_model.py” (a different one): add, commit, push, PR. Validate the modifications of your colleague and finish your own (add, commit, push, PR). After Pull Request, the following message appears: “this branch has conflicts that must be resolved”.

Handle conflict

On Github

Click on resolve conflicts. You will see the modifications brought by your branch and the other changes. Once you have solved the conflicts, click on mark as resolved.

Locally

When you merge the files, Git indicates the presence of a conflict. Three possibilities exist:

  • open the file locally and solve the conflict.
  • preserve the local modifications with git checkout --ours file
  • overwrite the local modifications and preserve the remote ones with git checkout --theirs file

Modification of the historic with git rebase

You have created a branch “Branch1” but during this time that main branch has been updated (let’s say the correction of a major bug). You have two possibilies:

  • on the branch “Branch1”, you merge the main branch. The drawback of this strategy is to create a complex historic.
  • with the command git rebase you overwrite the historic. Let’s illustrate this command.

Create a new branch “Branch1” and a new file “branch1_file.txt” and commit it. Return on the main branch, create a new file and commit it. Return on the branch “Branch1” and type:

$ git rebase main

This indicates that the last commit of main becomes the parent of the branch “Branch1”.

Warning: Do not rebase a public branch!

Back to top