Git Usage¶
Note
For detailed information on Git and Gitlab checkout the official Git and GitLab help page. Also, for good GitLab workflow you can checkout the Introduction to GitLab Flow (FREE) page.
These are (draft) general guidelines taken from BioPython project to be used for BeagleBoard development using git. We’re still working on the finer details.
This document is meant as an outline of the way BeagleBoard projects are developed. It should include all essential technical information as well as typical procedures and usage scenarios. It should be helpful for core developers, potential code contributors, testers and everybody interested in BeagleBoard code.
Note
This version is an unofficial draft and is subject to change.
Relevance¶
This page is about actually using git for tracking changes.
If you have found a problem with any BeagleBoard project, and think you know how to fix it, then we suggest following the simple route of filing a bug and describe your fix. Ideally, you would upload a patch file showing the differences between the latest version of BeagleBoard project (from our repository) and your modified version. Working with the command line tools diff and patch is a very useful skill to have, and is almost a precursor to working with a version control system.
Technicalities¶
This section describes technical introduction into git usage including required software and integration with GitLab. If you want to start contributing to BeagleBoard, you definitely need to install git and learn how to obtain a branch of the BeagleBoard project you want to contribute. If you want to share your changes easily with others, you should also sign up for a BeagleBoard GitLab account and read the corresponding section of the manual. Finally, if you are engaged in one of the collaborations on experimental BeagleBoard modules, you should look also into code review and branch merging.
Installing Git¶
You will need to install Git on your computer. Git is available for all major operating systems. Please use the appropriate installation method as described below.
Linux¶
Git is now packaged in all major Linux distributions, you should find it in your package manager.
Ubuntu/Debian¶
You can install Git from the git-core package. e.g.,
sudo apt-get install git-core
You’ll probably also want to install the following packages: gitk, git-gui, and git-doc
Redhat/Fedora/Mandriva¶
git is also packaged in rpm-based linux distributions.
dnf install gitk
should do the trick for you in any recent fedora/mandriva or derivatives
Mac OS X¶
Download the .dmg disk image from http://code.google.com/p/git-osx-installer/
Windows¶
Download the official installers from Windows installers
Testing your git installation¶
If your installation succeeded, you should be able to run
$ git --help
in a console window to obtain information on git usage. If this fails, you should refer to git documentation for troubleshooting.
Creating a GitLab account (Optional)¶
Once you have Git installed on your machine, you can obtain the code and start developing. Since the code is hosted at GitLab, however, you may wish to take advantage of the site’s offered features by signing up for a GitLab account. While a GitLab account is completely optional and not required for obtaining the BeagleBoard code or participating in development, a GitLab account will enable all other BeagleBoard developers to track (and review) your changes to the code base, and will help you track other developers’ contributions. This fosters a social, collaborative environment for the BeagleBoard community.
If you don’t already have a GitLab account, you can create one here. Once you have created your account, upload an SSH public key by clicking on SSH and GPG keys <https://git.beagleboard.org/-/profile/keys> after logging in. For more information on generating and uploading an SSH public key, see this GitLab guide.
Working with the source code¶
In order to start working with the BeagleBoard source code, you need to obtain a local clone of our git repository. In git, this means you will in fact obtain a complete clone of our git repository along with the full version history. Thanks to compression, this is not much bigger than a single copy of the tree, but you need to accept a small overhead in terms of disk space.
There are, roughly speaking, two ways of getting the source code tree onto your machine: by simply “cloning” the repository, or by “forking” the repository on GitLab. They’re not that different, in fact both will result in a directory on your machine containing a full copy of the repository. However, if you have a GitLab account, you can make your repository a public branch of the project. If you do so, other people will be able to easily review your code, make their own branches from it or merge it back to the trunk.
Using branches on GitLab is the preferred way to work on new features for BeagleBoard, so it’s useful to learn it and use it even if you think your changes are not for immediate inclusion into the main trunk of BeagleBoard. But even if you decide not to use GitLab, you can always change this later (using the .git/config file in your branch.) For simplicity, we describe these two possibilities separately.
Cloning BeagleBoard directly¶
Getting a copy of the repository (called “cloning” in Git terminology) without GitLab account is very simple:
git clone https://git.beagleboard.org/docs/docs.beagleboard.io.git
This command creates a local copy of the entire BeagleBoard repository on your machine (your own personal copy of the official repository with its complete history). You can now make local changes and commit them to this local copy (although we advise you to use named branches for this, and keep the main branch in sync with the official BeagleBoard code).
If you want other people to see your changes, however, you must publish your repository to a public server yourself (e.g. on GitLab).
Forking BeagleBoard with your GitLab account¶
If you are logged in to GitLab, you can go to the BeagleBoard Docs repository page:
https://git.beagleboard.org/docs/docs.beagleboard.io/-/tree/main
and click on a button named ‘Fork’. This will create a fork (basically a copy) of the official BeagleBoard repository, publicly viewable on GitLab, but listed under your personal account. It should be visible under a URL that looks like this:
https://git.beagleboard.org/yourusername/docs.beagleboard.io/
Since your new BeagleBoard repository is publicly visible, it’s considered good practice to change the description and homepage fields to something meaningful (i.e. different from the ones copied from the official repository).
If you haven’t done so already, setup an SSH key and upload it to gitlab for authentication.
Now, assuming that you have git installed on your computer, execute the following commands locally on your machine. This “url” is given on the GitLab page for your repository (if you are logged in):
git clone https://git.beagleboard.org/yourusername/docs.beagleboard.io.git
Where yourusername, not surprisingly, stands for your GitLab username. You have just created a local copy of the BeagleBoard Docs repository on your machine.
You may want to also link your branch with the official distribution (see below on how to keep your copy in sync):
git remote add upstream https://git.beagleboard.org/docs/docs.beagleboard.io/
If you haven’t already done so, tell git your name and the email address you are using on GitLab (so that your commits get matched up to your GitLab account). For example,
git config --global user.name "David Jones" config --global user.email "d.jones@example.com"
Making changes locally¶
Now you can make changes to your local repository - you can do this offline, and you can commit your changes as often as you like. In fact, you should commit as often as possible, because smaller commits are much better to manage and document.
First of all, create a new branch to make some changes in, and switch to it:
git branch demo-branch checkout demo-branch
To check which branch you are on, use:
git branch
Let us assume you’ve made changes to the file beaglebone-black/ch01.rst Try this:
git status
So commit this change you first need to explicitly add this file to your change-set:
git add beaglebone-black/ch01.rst
and now you commit:
git commit -m "added updates X in BeagleBone Black ch01"
Your commits in Git are local, i.e. they affect only your working branch on your computer, and not the whole BeagleBoard tree or even your fork on GitLab. You don’t need an internet connection to commit, so you can do it very often.
Pushing changes to GitLab¶
If you are using GitLab, and you are working on a clone of your own branch, you can very easily make your changes available for others.
Once you think your changes are stable and should be reviewed by others, you can push your changes back to the GitLab server:
git push origin demo-branch
This will not work if you have cloned directly from the official BeagleBoard branch, since only the core developers will have write access to the main repository.
Merging upstream changes¶
We recommend that you don’t actually make any changes to the main branch in your local repository (or your fork onGitLab). Instead, use named branches to do any of your own work. The advantage of this approach it is the trivial to pull the upstream main (i.e. the official BeagleBoard branch) to your repository.
Assuming you have issued this command (you only need to do this once):
git remote add upstream https://git.beagleboard.org/docs/docs.beagleboard.io/
Then all you need to do is:
git checkout main pull upstream main
Provided you never commit any change to your local main branch, this should always be a simple fast forward merge without any conflicts. You can then deal with merging the upstream changes from your local main branch into your local branches (and you can do that offline).
If you have your repository hosted online (e.g. at GitLab), then push the updated main branch there:
git push origin main
Submitting changes for inclusion in BeagleBoard¶
If you think you changes are worth including in the main BeagleBoard distribution, then file an (enhancement) bug on our bug tracker, and include a link to your updated branch (i.e. your branch on GitLab, or another public Git server). You could also attach a patch to the bug. If the changes are accepted, one of the BeagleBoard developers will have to check this code into our main repository.
On GitLab itself, you can inform keepers of the main branch of your changes by sending a ‘pull request’ from the main page of your branch. Once the file has been committed to the main branch, you may want to delete your now redundant bug fix branch on GitLab.
If other things have happened since you began your work, it may require merging when applied to the official repository’s main branch. In this case we might ask you to help by rebasing your work:
git fetch upstream checkout demo-branch
git rebase upstream/main
Hopefully the only changes between your branch and the official repository’s main branch are trivial and git will handle everything automatically. If not, you would have to deal with the clashes manually. If this works, you can update the pull request by replacing the existing (pre-rebase) branch:
git push origin demo-branch --force
If however the rebase does not go smoothly, give up with the following command (and hopefully the BeagleBoard developers can sort out the rebase or merge for you):
git rebase --abort
Evaluating changes¶
Since git is a fully distributed version control system, anyone can integrate changes from other people, assuming that they are using branches derived from a common root. This is especially useful for people working on new features who want to accept contributions from other people.
This section is going to be of particular interest for the BeagleBoard core developers, or anyone accepting changes on a branch.
For example, suppose Jason has some interesting changes on his public repository:
https://git.beagleboard.org/jkridner/docs.beagleboard.io
You must tell git about this by creating a reference to this remote repository:
git remote add jkridner https://git.beagleboard.org/jkridner/BeagleBoard.git
Now we can fetch all of Jason’s public repository with one line:
git fetch jkridner
Now we can run a diff between any of our own branches and any of Jason’s branches. You can list your own branches with:
git branch
Remember the asterisk shows which branch is currently checked out.
To list the remote branches you have setup:
git branch -r
For example, to show the difference between your main branch and Jason’s main branch:
git diff main jkridner/main
If you are both keeping your main branch in sync with the upstream BeagleBoard repository, then his main branch won’t be very interesting. Instead, try:
git diff main jkridner/awesomebranch
You might now want to merge in (some) of Jason’s changes to a new branch on your local repository. To make a copy of the branch (e.g. awesomebranch) in your local repository, type:
git checkout --track jkridner/awesomebranch
If Jason is adding more commits to his remote branch and you want to update your local copy, just do:
git checkout awesomebranch # if you are not already in branch awesomebranch pull
If you later want to remove the reference to this particular branch:
git branch -r -d jkridner/awesomebranch
Deleted remote branch jkridner/awesomebranch (#######)
Or, to delete the references to all of Jason’s branches:
git remote rm jkridner
git branch -r
upstream/main
origin/HEAD
origin/main
Alternatively, from within GitLab you can use the fork-queue to cherry pick commits from other people’s forked branches. While this defaults to applying the changes to your current branch, you would typically do this using a new integration branch, then fetch it to your local machine to test everything, before merging it to your main branch.
Committing changes to main branch¶
This section is intended for BeagleBoard developers, who are allowed to commit changes to the BeagleBoard main “official” branch. It describes the typical activities, such as merging contributed code changes both from git branches and patch files.
Prerequisites¶
Currently, the main BeagleBoard branch is hosted on GitLab. In order to make changes to the main branch you need a GitLab account and you need to be added as a collaborator/Maintainer to the BeagleBoard account. This needs to be done only once. If you have a GitLab account, but you are not yet a collaborator/Maintainer and you think you should be ask Jason to be added (this is meant for regular contributors, so in case you have only a single change to make, please consider submitting your changes through one of developers).
Once you are a collaborator/Maintainer, you can pull BeagleBoard official branch using the private url. If you want to make a new repository (linked to the main branch), you can just clone it:
git clone https://git.beagleboard.org/lorforlinux/docs.beagleboard.io.git
It creates a new directory “BeagleBoard” with a local copy of the official branch. It also sets the “origin” to the GitLab copy This is the recommended way (at least for the beginning) as it minimizes the risk of accidentally pushing changes to the official GitLab branch.
Alternatively, if you already have a working git repo (containing your branch and your own changes), you can add a link to the official branch with the git “remote command”… but we’ll not cover that here.
In the following sections, we assume you have followed the recommended scenario and you have the following entries in your .git/config file:
[remote "origin"]
url = https://git.beagleboard.org/lorforlinux/docs.beagleboard.io.git
[branch "main"]
remote = origin
Committing a patch¶
If you are committing from a patch, it’s also quite easy. First make sure you are up to date with official branch:
git checkout main pull origin
Then do your changes, i.e. apply the patch:
patch -r someones_cool_feature.diff
If you see that there were some files added to the tree, please add them to git:
git add beaglebone-black/some_new_file
Then make a commit (after adding files):
git commit -a -m "committed a patch from a kind contributor adding feature X"
After your changes are committed, you can push toGitLab:
git push origin
Tagging the official branch¶
If you want to put tag on the current BeagleBoard official branch (this is usually done to mark a new release), you need to follow these steps:
First make sure you are up to date with official branch:
git checkout main pull origin
Then add the actual tag:
git tag new_release
And push it to GitLab:
git push --tags origin main
Additional Resources¶
There are a lot of different nice guides to using Git on the web: