Stephanie M. Sherman, Ph.D.

Goals

• Understand the difference between the local and remote repository
• Understand branches
• Move a commit from the working directory to the remote repository
• Merge and update branches

Lesson

Understand the difference between the local and remote repository

• Let’s say we have a repo called learning_git and a branch called hotfix/add_docstring
• Look on bitbucket at the Branches and see how there is a branch called hotfix/add_docstring
• In a terminal in the learning_git repo type:

git branch

• Why do you only see the master branch?¹
• Let’s get the branch

git fetch origin hotfix/add_docstring

• Now you not only have the master branch but you also have the branch called hotfix/add_docstring in your local repository.
• Why do you have to include origin in the command?²

Understand branches

• A branch is an independent line of development
• Look at the utility module (utility.py)
• In a terminal in the learning_git repo type:

git checkout hotfix/add_docstring

• The local utility module changed and now reflects the contents of the branch hotfix/add_docstring
• Switch back and forth between the master and hotfix/add_docstring branch to understand what is happening.
• Let me demonstrate how to modify the branch
  1. Make a change. Where does the change exist?³
  2. Stage the change – git add modules/utility/utility.py
  3. Commit the changes to the local repository git commit -m 'making change'
     • Is the change in origin/remote repo?⁴
  4. Push the change – git push origin hotfix/add_docstring

Exercise 1

• Go back to the master branch
• Create your own branch called {first name}_{last name}_branch (e.g. git branch stephanie_sherman_branch)
• Switch to your branch
• Add the function below to your branch in the utility.py module
  • Place this code two lines below the say_hello() function

def say_goodbye(name):
    goodbye_string = f'Goodbye {name}'
    return goodbye_string

• Commit this function to the remote repo
• Go to bitbucket and see your change

Check Understanding

• You should now be able to:
  • create a branch
  • make a change
  • move that change from your working folder to the remote repository

Merge and update branches

• Let’s say one of your teammates completed code review on the hotfix/add_docstring branch and it is ready to be incorporated into the master branch (I will merge it now).
• Now, there are changes in master that are not included in your branch.
• Let’s get our branch up-to-date with the master branch by merging master into our branch

git merge master

• Why does git say it is already up to date?⁵
• Go to the Branches page and examine the “Ahead Behind” graphic of your branch
• Let’s switch to the master branch and get the changes

git checkout master
git pull origin master

• Open the utility.py module and verify that you have the updated changes
• Now that you have the updated changes it is time to add them to your branch

git checkout {first name}_{last name}_branch
git merge master

• Open the utility.py module and verify that you have the updated changes in the branch
• If I go to bitbucket would I see the changes in my branch?⁶

git push origin {first name}_{last name}_branch

• Now check bitbucket

Exercise 2

1. Get a teammate’s branch
2. Switch to that branch
3. Go to bitbucket and create a pull request on your branch and assign a reviewer.

Check Understanding

• You should now be able to:
  • Update any branch from remote
  • Fetch any branch from remote
  • Understand the beginning graphic

Bonus Material

Merge conflicts

• Sometimes the automated git merging strategies fail and require manual merging
• In bitbucket merge conflicts can be seen in pull requests diff

• Handling merge conflicts in your development branch may be the best approach
• Atom has a nice interface to manually resolve merge conflicts
• If you would like to use atom as your default editor open your .bash_profile in your home directory and add:

export EDITOR='atom'

• Open a new terminal (or source your .bash_profile)
• Merge master into the enhancement/if_time branch⁷
• Open atom and use the sidebar to examine the conflicts and navigate to them
• Click Use me to indicate which version of the code you would like to keep
• If you do not want to use either, right click on the dots next to Use me and click Dismiss. Be sure to delete the git syntax >>>>>>, <<<<<<<, =======
• After you resolve the conflict, stage your changes, commit, then push
• Now your branch should be ready to merge to master

example of the atom interface

Conflict Dividers

• <<<<<<< HEAD
• =======
• >>>>>>> <branch_to_merge>
• “The ======= line is the “center” of the conflict. All the content between the center and the <<<<<<< HEAD line is content that exists in the current branch master which the HEAD ref is pointing to. Alternatively all content between the center and >>>>>>> new_branch_to_merge_later is content that is present in our merging branch”

Helpful commands

1. git status : Show the files that are staged, unstaged, and untracked
2. git diff : Show unstaged changes in your working directory that are not yet in your local repo
   • You can always quit git diff by type q then return

Clean up

1. In order to walk through this tutorial again we need to revert back to the commit right before we started the lesson.

Answers

1: The hotfix/add_docstring is not located in your local repo until you fetch it from remote.
2: origin is shorthand for remote repository that a project was originally cloned (https://www.git-tower.com/learn/git/glossary/origin). In order to pull from remote you have specify it.
3: In the working directory
4: No, the change has not yet been pushed to remote, it only exists in your local repo
5: Our local repository does not have the updated changes. The changes only exist in remote.
6: No, the changes are only local they have not been pushed to remote
7: git merge master