--- title: Project management 2. Git continued marp: true paginate: true theme: buutti --- # Project management 2. Git continued ## Branches * A Git repository can have multiple ***branches*** * By default, a Git repository has only one branch * named either `master` or `main` * Using multiple branches makes it possible to work on new features step by step in their own ***feature branches*** * Meanwhile, the `master` branch is kept clean and in a working state * Only when the feature is completed, the branch is merged into the `master` branch! ![bg right:30% width: 60%](imgs/git-branches.png) ### Active branch * Even though your local repository can have multiple branches, only one of them is *active* at a given time * `git status` tells you firsthand which branch you are on: `On branch master` ## `git branch` & `git checkout` * You can create a new branch with `git branch ` * The new branch is not empty: it contains a copy of the code of the branch you executed this command in * ***Note:*** `git branch ` does not make the branch active! * To make the branch active, a.k.a "move" to the branch: * `git checkout `. * For example, to move back to master use `git checkout master` ### Local vs. remote branches * `git branch ` only creates a local branch * When you try to push changes from a new local branch, Git nags you that a matching remote branch doesn't yet exist * Git tells you how to create the remote branch: * `git push --set-upstream origin ` * Afterwards, `git push` pushes the changes to the matching remote branch ### Extra branch commands * Handy command: `git checkout -b ` * It's a shorthand for `git branch ` + `git checkout ` * Get a list of local branches with `git branch` * ...and all branches (incl. the remote ones) with `git branch -a` * Delete a local branch with `git branch -d ` * Remote branch can be deleted in the GitHub/etc website * ...or with `git push origin -d ` * ***Note:*** If deleted remote branches still show up in `git branch -a`, you can use the command `git remote prune origin` to remove them from the list. ## `git merge` * So you've been working on a feature branch. What next? * When the feature is done (and all the broken things fixed), you want to apply your changes back to `master` * For this, we use `git merge ` * It applies changes from `` to the ***current active branch*** * `master` branch is usually (and should be) protected, so we can't merge our new code to `master` directly * Instead, we do the *inverse*. ## Merging with a pull request 1) Make sure you have the newest version of the `master` branch: * Checkout `master` branch * Pull changes from GitHub/etc * Checkout the feature branch * Merge the contents of `master` to `featureBranch` with `git merge master` 2) Then, create a ***pull request*** on GitHub/etc (In GitLab, it's called ***merge request***!) * This creates a formal process for merging your *remote* feature branch to remote `master` * This adds a layer of protection to the `master` branch: no direct merging! --- ![](imgs/github-pullreq.png) * UI of a new pull request (*Pull requests > New pull request*) can be confusing... * *base* is the branch you're merging, *compare* is the branch you're merging into! ### If automatic merge fails... 1) Pull remote changes to your local `master`. * ***Pro tip:*** If you're on your feature branch, you can do this quickly without changing branches with ```git fetch origin master:master``` 2) Merge changes from `master` to your local feature branch. 3) Fix the ensuing ***conflicts*** (see [next section](#3-conflicts)) 4) Push your new local branch to GitHub/etc ## Extra: Merging without a pull request 1) First, checkout the `master` branch with `git checkout master` 2) Then, do a `git pull` so you have the newest version of the `master` branch * Someone else might have done changes to it while you were working on your feature! 3) Then, merge `` to `master` with `git merge ` * Fix conflicts ## Exercise 1. Pushing onwards Continue the exercise from [Git Basics](1-git-basics) or create a new repository for these exercises. * Create a new branch (with a name `new-feature`, for instance) in your local repository. * Checkout the branch, make some changes to `GitTest.md` there, and push the changes to GitHub. * Then, merge the changes from your `new-feature` branch to `master` branch by using a) pull request in GitHub b) `git merge` from command line ## GitLens * To make the Git workflow easier, install the GitLens extension to VS code * It helps in managing conflicts, comparing branches or commits * Install it from the Extensions panel (access with ***CTRL+SHIFT+X***) * Adds many new views to the source control tab: * Commits * Repositories * File History * Line History * Branches * Remotes * etc... # 3. Conflicts ## Conflicts * Sometimes two people have made changes in the same lines of code! * This leads to a conflict. * Let's assume we're trying to merge changes from featureBranch to master. * If a conflict happens, the merge does not conclude automatically. Instead, we need to ***fix all the conflicts*** by hand and then ***conclude the merge*** with some commands. * Conflicting lines of code are framed by some `<<<<<<< garbage ======= symbols >>>>>>>` we don't yet understand * Before we can conclude the merge, we need to get rid of the garbage. ### Said garbage ```c# <<<<<<< HEAD:Player.cs if (Input.anyKey) { return true; } ======= if (Input.anyKey) return true; >>>>>>> featureBranch:Player.cs ``` * ***Current change*** is between `<<<<<<<` and `=======`: old code in `master` * ***Incoming change*** is between `>>>>>>>` and `=======`: new code from `featureBranch` * Use your text editor to choose which (or some combination of both) you want to preserve ### VS Code tools * VS Code gives us tools to make conflict resolution a quick process * Click which lines of code you want to preserve: * ***Accept Current Change*** (old code is preserved, new code removed) * ***Accept Incoming Change*** (new code is preserved, old code removed) * ***Accept Both Changes*** (both are preserved) ![bg right width:95%](imgs/vscode-conflicts.png) ## After resolving the conflict * After resolving conflicting files, use `git add ` to add them to the commit * Then use `git commit` to apply changes (without a message! no `-m`) * Close the automatically opened `COMMITMSG` file. This should finish the merge. * Then just `git push` to apply changes in the remote repository ## Exercise 2. Fixing conflicts * Create a new branch in your local repository, but do not checkout it just yet. * First, we simulate your teammate's changes by making changes to the `master` branch directly: On the `master` branch, make some changes to `GitTest.md`, and **add & commit**. * Then, checkout the new feature branch. * Then, make some other changes to GitTest.md to the same line as before, **add & commit**. * Then, merge the changes from the `master` branch to your feature branch by using `git merge` * Fix the ensuing conflicts, add & commit & push. * Now you can create a pull request to merge your changes to the master branch. ## Git workflow 3: Undoing * Git doesn't have a general "undo" command * If you make a mistake, it is very case-specific what you need to do to fix it * See [undo options here](https://docs.gitlab.com/ee/topics/git/numerous_undo_possibilities_in_git/) * Also, [ohshitgit.com](https://ohshitgit.com/) ## `git log` & `git checkout ` * Use `git log` to see the commit history * Or `git log --oneline` for a more concise version * Press ***Q*** to quit the log view. * The newest changes are seen on top * On the left side of the commit message you see the ***hashcode*** of the commit * Use `git checkout ` to "time travel" into the commit * ***Note:*** If you have GitLens, check the Commits view in the Source control tab to see the commit history. ## Revert one file to a previous state * Sometimes you want to revert just one file to its previous state * For that, you need to figure out the commit hash of the state you want to return to * Find that out in one of the following methods: * `git log --oneline` * VS Code: *Source control > File history* * GitHub: check commits * Then, run * `git checkout -- ` ## Collaboration in Unity * ***The zeroth rule:*** Make sure that everyone on team uses the same Unity and package versions. * ***The first rule:*** Don't ever work on the same thing simultaneously. * ***The second rule:*** When you do break rule #1, make necessary changes in communication so you won't break it again. * Be sure to communicate about ***scene ownership*** * Scenes are not code files, so you can't easily merge changes if two people have worked on them * Thus, the ***Scene Owner*** will be the only person on the team who should be working on a certain scene * If a scene needs GameObject contributions from others, they can create prefabs that the Scene Owners then add to their scene ## Exercise 3. Branching team effort * Work as a group for this assignment. * Continue Exercise 2 from [Git basics](1-git-basics). * Every group member creates an individual branch from the master, and makes some changes to the `GitTest.md` file. * Add new files as well, at least one per group member. * Do not tell other group members what you're going to change! :D * Then, merge the changes back to the master branch. Fix ensuing conflicts, if any appear. ## Reading * [Pro Git book](https://git-scm.com/book/en/v2) * [Oh shit Git](https://ohshitgit.com/) * [Undo possibilities](https://docs.gitlab.com/ee/topics/git/numerous_undo_possibilities_in_git/) ## Very extra: `git rebase` * `git merge` creates a new commit for the merge process * Sometimes that's undesirable, so an alternative is to use `git rebase` * Unlike merge, rebase applies changes from the rebased branch ***one commit at a time*** * Whenever there's a conflict: 1) After fixing the conflict, add the conflicting file with `git add ` 2) Then continue the rebase process with `git rebase --continue` 3) If you want to disregard a conflicting commit, use `git rebase --skip` 4) If you get cold feet, you can cancel the rebase with `git rebase --abort` * ***Note:*** A good link for [understanding rebase](https://borbware.github.io/unity-basics-course/project-management/2-git-continued-slides.html) ## Very very extra: Git submodules * To add external code to your project from someone else's repository, Git has a neat system called *submodules* * To add a submodule to your project, use `git submodule add ` * To remove a submodule, use `git rm ` * If you clone a project with submodules, you need to run `git submodule update --init --recursive` once. * ***Note:*** If you don't want submodules to appear in the Source control tab of VS Code, go to settings and disable the *Git: Detect Submodules* setting.