### create a new repository create a new directory, open it and perform `git init` to create a new git repository ```bash git init ``` ### checkout a respository Create a working copy of a local repository by running the command: ```bash git clone /path/to/repository ``` when using a remote server, your command will be ```bash git clone username@host:/path/to/repository ``` ### workflow Your local repository consists of three "trees" maintained by git. The first one is your `Working Directory`, which holds the actual files. The second one is the `Index`, which acts as a staging area, and, finally, the `HEAD`, which points to the last commit you've made. ![[trees.png]] ### add & commit You can propose changes (add it to the **Index**) using `git add <filename`. This is the first step in the basic git workflow. ```bash git add <filename> git add * ``` To actually commit these changes use: ```bash git commit -m "Commit message" ``` Now the file is committed to the **HEAD**, but not in your remote repository yet. ### pushing changes Your changes are now in the **HEAD** of your local working copy. To send those changes to your remote repository, execute: ```bash git push origin main ``` **Note**: Change _main_ to whatever branch you want to push your changes to. If you have not cloned an existing repository and want to connect your repository to a remote server, you need to add it with: ```bash git remote add origin <server> ``` Now you are able to push your changes to the selected remote server ### branching Branches are used to develop features isolated from each other. The _master_ branch is the "default" branch when you create a repository. Use other branches for development and merge them back to the master branch upon completion. ![[branches.png]] Create a new branch named "feature_x" and switch to it using: ```bash git checkout -b feature_x ``` switch back to main: ```bash git checkout main ``` and delete the branch again: ```bash git branch -d feature_x ``` A branch is _not available to others_ unless you push the branch to your remote repository: ```bash git push origin <branch> ``` ### update & merge To update your local repository to the newest commit, execute `git pull` in your working directory to _fetch_ and _merge_ remote changes. ```bash git pull ``` To merge another branch into your active branch (e.g. main), use: ```bash git merge <branch> ``` In both cases git tries to auto-merge changes. Unfortunately, this is not always possible and results in _conflicts_. You are responsible to merge those _conflicts_ manually by editing the files shown by git. After changing, you need to mark them as merged with: ```bash git add <filename> ``` Before merging changes, you can also preview them by using: ```bash git diff <source_branch> <target_branch> ``` ### tagging It's recommended to create tags for software releases. this is a known concept, which also exists in SVN. You can create a new tag named _1.0.0_ by executing `git tag 1.0.0 1b2e1d63ff` the _1b2e1d63ff_ stands for the first 10 characters of the commit id you want to reference with your tag. You can get the commit id by looking at the log (see below) ### log In its simplest form, you can study repository history using `git log` You can add a lot of parameters to make the log look like what you want. To see only the commits of a certain author: ```bash\ git log --author=bob ``` To see a very compressed log where each commit is one line: ```bash git log --pretty=oneline ``` Or maybe you want to see an ASCII art tree of all the branches, decorated with the names of tags and branches: ```bash git log --graph --oneline --decorate --all ``` See only which files have changed: ```bash git log --name-status ``` These are just a few of the possible parameters you can use. For more, see `git log --help` ### replace local changes In case you did something wrong, you can replace local changes using the command: ```bash git checkout -- <filename> ``` `git checkout -- <filename>` replaces the changes in your working tree with the last content in HEAD. Changes already added to the index, as well as new files, will be kept. If you instead want to drop all your local changes and commits, fetch the latest history from the server and point your local master branch at it like this: ```bash git fetch origin git reset --hard origin/master ``` ### useful hints built-in git GUI ```bash gitk ``` use colorful git output ```bash git config color.ui true ``` show log on just one line per commit ```bash git config format.pretty oneline ``` use interactive adding ```bash git add -i ```