assistant: Development is done using the Git distributed version control system. Thus, access to the repository is not strictly necessary. We welcome contributions in the form of patches as produced by git format-patch sent to the guix-patches@gnu.org mailing list (see Submitting patches to a project in Git User Manual). Contributors are encouraged to take a moment to set some Git repository options (see Configuring Git) first, which can improve the readability of patches. Seasoned Guix developers may also want to look at the section on commit access (see Commit Access).

This mailing list is backed by a Debbugs instance, which allows us to keep track of submissions (see Tracking Bugs and Patches). Each message sent to that mailing list gets a new tracking number assigned; people can then follow up on the submission by sending email to ISSUE_NUMBER@debbugs.gnu.org, where ISSUE_NUMBER is the tracking number (see Sending a Patch Series).

Please write commit logs in the ChangeLog format (see Change Logs in GNU Coding Standards); you can check the commit history for examples.

Before submitting a patch that adds or modifies a package definition, please run through this check list:

If the authors of the packaged software provide a cryptographic signature for the release tarball, make an effort to verify the authenticity of the archive. For a detached GPG signature file this would be done with the gpg --verify command.
Take some time to provide an adequate synopsis and description for the package. See Synopses and Descriptions, for some guidelines.
Run guix lint package, where package is the name of the new or modified package, and fix any errors it reports (see Invoking guix lint).
Run guix style package to format the new package definition according to the project’s conventions (see Invoking guix style).
Make sure the package builds on your platform, using guix build package.
We recommend you also try building the package on other supported platforms. As you may not have access to actual hardware platforms, we recommend using the qemu-binfmt-service-type to emulate them. In order to enable it, add the virtualization service module and the following service to the list of services in your operating-system configuration:

(service qemu-binfmt-service-type
 (qemu-binfmt-configuration
   (platforms (lookup-qemu-platforms "arm" "aarch64"))))

Then reconfigure your system.

You can then build packages for different platforms by specifying the --system option. For example, to build the "hello" package for the armhf or aarch64 architectures, you would run the following commands, respectively:

guix build --system=armhf-linux --rounds=2 hello
guix build --system=aarch64-linux --rounds=2 hello

Make sure the package does not use bundled copies of software already available as separate packages.
Sometimes, packages include copies of the source code of their dependencies as a convenience for users. However, as a distribution, we want to make sure that such packages end up using the copy we already have in the distribution, if there is one. This improves resource usage (the dependency is built and stored only once), and allows the distribution to make transverse changes such as applying security updates for a given software package in a single place and have them affect the whole system—something that bundled copies prevent.

Take a look at the profile reported by guix size (see Invoking guix size). This will allow you to notice references to other packages unwillingly retained. It may also help determine whether to split the package (see Packages with Multiple Outputs), and which optional dependencies should be used. In particular, avoid adding texlive as a dependency: because of its extreme size, use the texlive-tiny package or texlive-union procedure instead.
For important changes, check that dependent packages (if applicable) are not affected by the change; guix refresh --list-dependent package will help you do that (see Invoking guix refresh).
Depending on the number of dependent packages and thus the amount of rebuilding induced, commits go to different branches, along these lines:

300 dependent packages or less
master branch (non-disruptive changes).

between 300 and 1,800 dependent packages
staging branch (non-disruptive changes). This branch is intended to be merged in master every 6 weeks or so. Topical changes (e.g., an update of the GNOME stack) can instead go to a specific branch (say, gnome-updates). This branch is not expected to be buildable or usable until late in its development process.

more than 1,800 dependent packages
core-updates branch (may include major and potentially disruptive changes). This branch is intended to be merged in master every 6 months or so. This branch is not expected to be buildable or usable until late in its development process.

All these branches are tracked by our build farm and merged into master once everything has been successfully built. This allows us to fix issues before they hit users, and to reduce the window during which pre-built binaries are not available.

When we decide to start building the staging or core-updates branches, they will be forked and renamed with the suffix -frozen, at which time only bug fixes may be pushed to the frozen branches. The core-updates and staging branches will remain open to accept patches for the next cycle. Please ask on the mailing list or IRC if unsure where to place a patch.

Check whether the package’s build process is deterministic. This typically means checking whether an independent build of the package yields the exact same result that you obtained, bit for bit.
A simple way to do that is by building the same package several times in a row on your machine (see Invoking guix build):

guix build --rounds=2 my-package

This is enough to catch a class of common non-determinism issues, such as timestamps or randomly-generated output in the build result.

Another option is to use guix challenge (see Invoking guix challenge). You may run it once the package has been committed and built by ci.guix.gnu.org to check whether it obtains the same result as you did. Better yet: Find another machine that can build it and run guix publish. Since the remote build machine is likely different from yours, this can catch non-determinism issues related to the hardware—e.g., use of different instruction set extensions—or to the operating system kernel—e.g., reliance on uname or /proc files.

When writing documentation, please use gender-neutral wording when referring to people, such as singular “they”, “their”, “them”, and so forth.
Verify that your patch contains only one set of related changes. Bundling unrelated changes together makes reviewing harder and slower.
Examples of unrelated changes include the addition of several packages, or a package update along with fixes to that package.

Please follow our code for GUIX formatting rules, possibly running guix style script to do that automatically for you.
When possible, use mirrors in the source URL (see Invoking guix download). Use reliable URLs, not generated ones. For instance, GitHub archives are not necessarily identical from one generation to the next, so in this case it’s often better to clone the repository. 
Don’t use the name field in the URL: it is not very useful and if the name changes, the URL will probably be wrong.
Check if Guix builds (see Building from Git) and address the warnings, especially those about use of undefined symbols.
Make sure your changes do not break Guix and simulate a guix pull with:

guix pull --url=/path/to/your/checkout --profile=/tmp/guix.master

When posting a patch to the mailing list, use ‘[PATCH] …’ as a subject, if your patch is to be applied on a branch other than master, say core-updates, specify it in the subject like ‘[PATCH core-updates] …’.

You may use your email client or the git send-email command (see Sending a Patch Series). We prefer to get patches in plain text messages, either inline or as MIME attachments. You are advised to pay attention if your email client changes anything like line breaks or indentation which could potentially break the patches.

Expect some delay when you submit your very first patch to guix-patches@gnu.org. You have to wait until you get an acknowledgement with the assigned tracking number. Future acknowledgements should not be delayed.

[information pulled from https://guix.gnu.org/manual/en/html_node/Submitting-Patches.html]