Currently Online

Latest Posts

GitPrimer

We'll be moving everything except for widelands-media to GitHub. This page explains how to obtain the source code and how to work with it. We are prodiving instructions for how to do it on the command line / in a terminal, but we recommend that you also use a GUI client to make your life easier.

Main differences to bazaar

When using bazaar, you probably have each branch in it's own directory. When using git, you have only one directory. git handles all branches in this directory and changing to a branch is done with the command git checkout BRANCHNAME. This command applies the changes made in BRANCHNAME to the files in this directory. E.g. the command git checkout master revert all files in this directory to the state of the master branch.

Installing Git

First, you will need to download install Git on your machine. Follow the instructions on the Git Downloads page. We also recommend that you get a GUI client.

Getting the Source Code

Rather than working on the Widelands repository directly, you will create your own fork, work on a branch there and then make a Pull Request when your code is ready. If you don't expect to be working on the code and only want to play the development version, call git clone https://github.com/widelands/widelands.git --depth 1 on the command line and you're done.

1. Create a fork

  1. Visit https://github.com/widelands and pick the repository that you want to clone. For the Widelands game, this will be "widelands". We will be using this as an example throughout, but it works the same for all our repositories.
  2. Hit the "Fork" button. This will create a new Git repository on GitHub at <username>/widelands that links back to widelands/widelands on the GitHub website.

2. Download the code

We want to set up both your fork ("origin") and the original ("upstream") repository on your machine. Your fork is for you to work on, and the upstream repository is for keeping up with the changes in our master branch. We will also be using the "depth" parameter to speed things up - if you want the full commit history, just leave it out.

  1. Open a command line / terminal and cd to where you want to clone widelands.
  2. Visit <username>/widelands on GitHub and locate the green "Clone or download" button. This will give you a link to copy that looks like https://github.com/<userame>/widelands.git.
  3. Paste the link that you just copied to run git clone https://github.com/<userame>/widelands.git --depth 500 on your command line / in your terminal. This will pull your fork down onto your machine and check out the master branch. Your fork will be known as origin to the Git system.
  4. Repeat step 2 with the original repository on GitHub. The link will look like https://github.com/widelands/widelands.git --depth 500
  5. Link up the original by running git remote add upstream https://github.com/widelands/widelands.git. This will now be known as upstream to the Git system.

In principle, you can add as many forks as you want and call them anything you want. You can get a list by running git remote -v.

Note: If you don't need the whole git history, you can create a shallow clone by calling git clone https://github.com/<userame>/widelands.git --depth 1

Working on and contributing code

If you plan to be working on multiple branches at the same time, see Checking out into subdirectories - we haven't worked out the details of that one yet, so please feel free to contribute to this Wiki page.

1. Create a branch

You should always work in a separate branch for each feature and never on the master branch. For creating a branch, run git checkout -b <branch_name>.

2. Commit and upload your changes

You should always keep in sync with upstream's master branch. Call git pull upstream master and follow the instructions. Once you feel comfortable with Git, you can also consider rebasing instead.

After BuildingWidelands and making your changes, you can do a local commit.

  1. You can see which files have changed by running git status and see a diff by running git diff.
  2. Note: Unlike Bazaaar where you only need to bzr add new files, you will need to run git add for all the files that have any changes in them! This is the bit where we recommend using a GUI client.
  3. After running git add for your changes, you can commit them by running git commit -m "Commit message". Reference the issue that your working on with #, e.g. "Fixes #123". This will link your branch to issue No. 123 in the GitHub issue tracker.
  4. Finally, push your changes with git push origin <branch_name>.

Note: If you did not add any new files, you cann add and commit at the same time by running git commit -am "Commit message".

3. Get your changes into the game

Once you are happy with your branch, it's time to hit the "Pull Request" button on GitHub, so that your branch will be merged into our master branch.

  • Describe what your change does
  • If your branch adresses any of our issues, mention the issue(s)
  • Your pull request and each subsequent push to your branch will trigger automated builds on Travis and AppVeyor. Check out the protocols for these builds to see if they were successful and whether there are any new compiler warnings or test failures to fix.
  • GitHub will also send you an e-mail when a reviewer adds a comment.

Comparison with Bazaar

Action bzr git
Switch to trunk cd ../trunk git checkout master
Update trunk and merge into local branch cd ../trunk; bzr pull lp:widelands; cd ../<branch>; bzr merge ../trunk; bzr commit -m "Merged trunk." git pull --rebase upstream master; git push origin <branch> --force
Show branches, with the current one highlighted Use operating system to list directories git branch
Delete remote branch Use Launchpad interface git push origin --delete <branch_name>
Delete local branch Use operating system to delete directory git branch -d <branch_name>
Undo all changes bzr revert git checkout .
Undo changes to a file bzr revert <file> git checkout <file>
Get a remote branch and switch to it bzr branch <remote_branch_name> <new_local_branch>; cd <new_local_branch> git checkout -b <new_local_branch> <remote_location>/<remote_branch_name>

See also Merging in bzr: The git approach vs the bzr approach

Workflow

Getting the code

fork_and_clone.png

Working on your code

git_commit_cycle.png

Synchonizing with the main repository / master branch

Merging

git_merge_forkflow.png

Rebasing

git_rebase_forkflow.png

Checking out into subdirectories

Since our bottleneck is compile time rather than disk space, we will want to be able to check out into subdirectories, just like Bazaar does it. There are 2 ways of doing this:

  1. Clone the full repository into a new directory and set up the remotes each time. This will support submodules (we are currently not using submodules, so don't worry about this). This will be very time/bandwith consumig as the whole repo will be transfered again. Instead of cloning every time, you can also duplicate your master directory manually (cp -r widelands <branchname>) which is usually faster and requires no bandwidth.
  2. Use git worktree (manual blog). This command will create a separate copy of submodules too, but can handle only 1 level.

Using ssh instead of https

Tired of typing your pasword all the time? If so, this section is for you.

If you do not have an SSH key already, follow the instructions on GitHub. If you already have a public ssh key, you can reuse it with GitHub.

  • Upload the public key to your settings.
  • Once provided you can use ssh instead of https for every GitHub related command e.g. git clone git@github.com:widelands/widelands.git
  • The GitHub GUI provides the needed path when you click on "clone or download" on the repository page

Checking out a branch from somebody else's fork

$ git clone https://github.com/widelands/widelands.git --depth 1
$ cd widelands/
$ git remote add niftyfork https://github.com/niftyfork/widelands.git
$ git fetch niftyfork --depth 1
$ git checkout niftybranch

The last message you see should be:

Branch 'niftybranch' set up to track remote branch 'niftybranch' from 'niftyfork'.
Switched to a new branch 'niftybranch'

And this is what the commands mean:

$ git clone https://github.com/widelands/widelands.git --depth 1
$ cd widelands/

Clone the main Widelands repository and change into its directory. You only need to do this if you haven't already. --depth 1 means you only fetch the latest revision, which will speed things up. YOu can omit that if you want to get the complete commit history.

$ git remote add niftyfork https://github.com/niftyfork/widelands.git

Register niftyfork's fork and call it "niftyfork"

$ git fetch niftyfork  --depth 1

Register what's in niftyfork's fork. Again, --depth 1 will speed things up. Git should tell you about the branches that it has found at this point.

$ git checkout niftybranch

Switch to the branch.

If you want to change forks for your local branch, call

git branch -u otherniftyfork/niftybranch

Checkout out and tracking a remote branch

This is how to checkout a remote branch from a specific fork and register it as the push and pull location for the branch. First, you get the information about the branches in the fork and their status:

$ git fetch niftyfork

Then you switch to the branch while telling it to track the remote source:

git checkout -t niftyfork/niftybranch 

Now you can push and pull by simply calling:

git push
git pull 

Useful Links and Tutorials