Cheat Sheet: Basic Git Commands

git add readme.md   # adds the changes of the file `readme.md` to the staging area
git add .           # adds all changes of files in the current directory (recursively) to the staging area
git add --all       # adds all changes of files in the repository to the staging area
git commit -a       # executes a commit that automatically stages all changed and deleted files before
git checkout -b     # Create a new local branch based on the current branch
git pull            # Pull changes from the current remote branch
git push            # Push changes to the current remote branch
git stash           # Puts all changes in an dirty wirkling directory aside
git stash apply     # Reapplies stashed changes on the current branch

Installation

If you are uncomfortable with command line interfaces, there are also plenty of GUI options available.

Basic Configuration

To configure git, you can use the git config command. You can configure each project individually, just by running git config <setting> <value> anywhere within a checked out repository, or for all projects for a user on the local machine using git config --global <setting> <value>. We recommend you set the following configuration options, when using git:

git config merge.ff false # Git will always create a commit, when trying to merge

git config pull.rebase true # Automatically rebase when pulling

Also ensure that you have your username and e-mail configured, so your work can be attributed to you:

git config --global user.name "Your Name"

git config --global user.email "yourname@yourdomain.com"

The Commit Message

A commit message should have the following syntax: component: short change description

For a clean and meaningful log the commit message should fulfill the following:

use imperative in the subject line
the subject line should not be longer than 50 characters
start the subject line with the module name (e.g. resolver:, cpp bindings:)
separate subject from body with a blank line
in the body describe in detail what you did, and possibly why
metadata like "Fixes #123" should be kept at the bottom of the commit message and definitely not in the title

Most commits should have a longer description in the body.

GitHub: Attributing Co-Authors

If multiple people worked on a commit, GitHub, supports a nice way to represent this. You can attribute them by leaving two blank lines at the end and then add a single line of Co-authored-by: NAME <NAME@EXAMPLE.COM> for every other person that worked on it. More Details here

Remote Branches

To list all remote branches use:

git branch -a

To checkout a remote branch initially use:

git checkout -b <branchname> origin/<branchname>

Once you have done this, it will be a local branch, too. Following remote branches should exist:

master

This is the development branch. Please try to not work directly on it, but instead you should use feature branches. So the only commits on master should be non-fastforward merges from features branches. Commits on master should always compile, and all test cases should pass successfully. (see config option above)

Communication Methods

To communicate with remote branches, Git supports the file protocol (acessible through the local file system), http and ssh. We generally recommend ssh, as it is encrypted and authentication with ssh-keys is simple and secure.

GitHub: Adding/creating an SSH Key

GitHub supports both HTTP and SSH for communication. Using SSH, you can remove the annoyance of having to enter your password every time. To learn how to add an SSH-Key follow this guide provided by GitHub.

Local Branches

You should always make your own feature branch with:

git checkout -b <feature-branch-name>

On this branch it is not so important that every commit compiles or all test cases run.

To merge a branch use (no-fastforward):

git merge --no-ff <branchname>

If you already did some commits, but want them in a branch, you can do:

git branch foo
git reset HEAD^^  # for 2 commits back
git reset origin/master
 
git-ref-log # recover

Working with forks

We recommend you use your own fork of the main libelektra repository, if you want to contribute. For more information on creating a fork, please take a look at GitHub's tutorial.

Once you have set up and cloned your fork, you need to keep it in sync with the main repository. To do that, we recommend you never directly commit anything to your fork's master branch. You also need to add a remote for the main repository:

# We assume the remote for your fork is called `origin` (the default).

git remote add upstream https://github.com/ElektraInitiative/libelektra.git

When you want to sync changes from the main repository into your fork, you can use these commands:

git fetch upstream master:master

git push orign master:master

Note: These commands work with any branch checked out. You don't need to switch to the master branch first. However, this only works, if you have not modified your master branch, i.e. the latest commit in your forked master branch was once the latest commit in the main master branch.

Rebasing branches

When you work on a local feature branch, it might happen that a change occurs within the master branch, that introduces merge conflicts. I.e. if you create a pull request, it cannot be merged into master automatically anymore. In these cases, we expect you to rebase your feature branch, so it can be merged automatically once again.

To achieve this, make sure you have your master branch synced up. Then switch to the feature branch you want to update using git checkout <feature-branch-name> and then type git rebase master. Sometimes, this will result in a merge conflict.

If you already have pushed changes from your feature branch to a remote branch, you'll need to either overwrite it using git push --force or push to a new remote branch.

Resolving merge conflicts

To resolve merge conflicts, edit the files that need to be merged manually. You can check which files need to be merged using git status. After you are done merging a file manually, you can use git add <path-to-file> and when you have merged all files, continue with git rebase --continue.

Note: Keep in mind that manual merges within a rebase are potentially destructive. If you accidentally remove changes you've done in your feature branch, you might be able to recover them using git-reflog, but they could also be deleted by the git-gc. If you're new to manually merging files, consider creating a new branch from your feature branch using git checkout -b <new-branch-name> on which you can perform the merge without risk. When you're stuck on a manual merge, you can also always abort the rebase using git rebase --abort