Moritz Poldrack 8c64bda5a0 doc: add contribution guidelines including code style
The Linux kernel code style rules have been used as a well-tested basis
and sections pertaining C-specific rules – such as macros – have been
removed. For it a short section on the used formatter is added for
further reference.

Signed-off-by: Moritz Poldrack <>
Signed-off-by: Robin Jarry <>
2022-08-05 21:57:12 +02:00

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Contribution Guidelines

This document contains guidelines for contributing code to aerc. It has to be followed in order for your patch to be approved and applied.

Contribution Channels

Anyone can contribute to aerc. First you need to clone the repository and build the project:

$ git clone
$ cd aerc
$ make

Patch the code. Write some tests. Ensure that your code is properly formatted with gofumpt. Ensure that everything builds and works as expected. Ensure that you did not break anything.

  • If applicable, update unit tests.
  • If adding a new feature, please consider adding new tests.
  • Do not forget to update the docs.
  • If your commit brings visible changes for end-users, add an entry in the Unreleased section of the file.
  • run the linter using make lint if notmuch is not available on your system you may have to edit .golangci.toml and disable the notmuch tag. Otherwise you could get hard to trace false positives

Once you are happy with your work, you can create a commit (or several commits). Follow these general rules:

  • Limit the first line (title) of the commit message to 60 characters.
  • Use a short prefix for the commit title for readability with git log --oneline.
  • Use the body of the commit message to actually explain what your patch does and why it is useful.
  • Address only one issue/topic per commit.
  • If you are fixing a ticket, use appropriate commit trailers.
  • If you are fixing a regression introduced by another commit, add a Fixes: trailer with the commit id and its title.

There is a great reference for commit messages in the Linux kernel documentation.

IMPORTANT: you must sign-off your work using git commit --signoff. Follow the Linux kernel developer's certificate of origin for more details. All contributions are made under the MIT license. If you do not want to disclose your real name, you may sign-off using a pseudonym. Here is an example:

Signed-off-by: Robin Jarry <>

Before sending the patch, you should configure your local clone with sane defaults:

$ git config format.subjectPrefix "PATCH aerc"
$ git config "~rjarry/"

And send the patch to the mailing list (step by step instructions):

$ git send-email --annotate -1

Before your patch can be applied, it needs to be reviewed and approved by others. They will indicate their approval by replying to your patch with a Tested-by, Reviewed-by or Acked-by (see also: the git wiki) trailer. For example:

Acked-by: Robin Jarry <>

There is no "chain of command" in aerc. Anyone that feels comfortable enough to "ack" or "review" a patch should express their opinion freely with an official Acked-by or Reviewed-by trailer. If you only tested that a patch works as expected but did not conduct a proper code review, you can indicate it with a Tested-by trailer.

You can follow the review process via email and on the web ui.

Wait for feedback. Address comments and amend changes to your original commit. Then you should send a v2 (and maybe a v3, v4, etc.):

$ git send-email --annotate -v2 -1

Be polite, patient and address all of the reviewers' remarks. If you disagree with something, feel free to discuss it.

Once your patch has been reviewed and approved (and if the maintainer is OK with it), it will be applied and pushed.

Code Style

Please refer only to the quoted sections when guidelines are sourced from outside documents as some rules of the source material may conflict with other rules set out in this document.


Indentation rules follow the Linux kernel coding style:

Tabs are 8 characters, and thus indentations are also 8 characters. […]

Rationale: The whole idea behind indentation is to clearly define where a block of control starts and ends. Especially when youve been looking at your screen for 20 straight hours, youll find it a lot easier to see how the indentation works if you have large indentations. — Linux kernel coding style

Breaking long lines and strings

Wrapping rules follow the Linux kernel coding style:

Coding style is all about readability and maintainability using commonly available tools.

The preferred limit on the length of a single line is 80 columns.

Statements longer than 80 columns should be broken into sensible chunks, unless exceeding 80 columns significantly increases readability and does not hide information. […] These same rules are applied to function headers with a long argument list.

However, never break user-visible strings such as printk messages because that breaks the ability to grep for them. — Linux kernel coding style

Whether or not wrapping lines is acceptable can be discussed on IRC or the mailing list, when in doubt.


Function rules follow the Linux kernel coding style:

Functions should be short and sweet, and do just one thing. They should fit on one or two screenfuls of text (the ISO/ANSI screen size is 80x24, as we all know), and do one thing and do that well.

The maximum length of a function is inversely proportional to the complexity and indentation level of that function. So, if you have a conceptually simple function that is just one long (but simple) case-statement, where you have to do lots of small things for a lot of different cases, its OK to have a longer function.

However, if you have a complex function, and you suspect that a less-than-gifted first-year high-school student might not even understand what the function is all about, you should adhere to the maximum limits all the more closely. Use helper functions with descriptive names (you can ask the compiler to in-line them if you think its performance-critical, and it will probably do a better job of it than you would have done).

Another measure of the function is the number of local variables. They shouldnt exceed 5-10, or youre doing something wrong. Re-think the function, and split it into smaller pieces. A human brain can generally easily keep track of about 7 different things, anything more and it gets confused. You know youre brilliant, but maybe youd like to understand what you did 2 weeks from now. — Linux kernel coding style


Function rules follow the Linux kernel coding style:

Comments are good, but there is also a danger of over-commenting. NEVER try to explain HOW your code works in a comment: its much better to write the code so that the working is obvious, and its a waste of time to explain badly written code.

Generally, you want your comments to tell WHAT your code does, not HOW. Also, try to avoid putting comments inside a function body: if the function is so complex that you need to separately comment parts of it, you should probably go back to [the previous section regarding functions] for a while. You can make small comments to note or warn about something particularly clever (or ugly), but try to avoid excess. Instead, put the comments at the head of the function, telling people what it does, and possibly WHY it does it.

When commenting […] API functions, please use the [GoDoc] format. See the official documentation for details. — Linux kernel coding style

Editor modelines

Some editors can interpret configuration information embedded in source files, indicated with special markers. For example, emacs interprets lines marked like this:

-*- mode: c -*-

Or like this:

Local Variables:
compile-command: "gcc -DMAGIC_DEBUG_FLAG foo.c"

Vim interprets markers that look like this:

/* vim:set sw=8 noet */

Do not include any of these in source files. People have their own personal editor configurations, and your source files should not override them. This includes markers for indentation and mode configuration. People may use their own custom mode, or may have some other magic method for making indentation work correctly. — Linux kernel coding style

In the same way, files specific to only your workflow (for example the .idea or .vscode directory) are not desired. If a script might be useful to other contributors, it can be sent as a separate patch that adds it to the contrib directory. Since it is not editor-specific, an .editorconfig is available in the repository.


The Go-code follows the rules of gofumpt which is equivalent to gofmt but adds a few additional rules. The code can be automatically formatted by running make fmt.

If gofumpt accepts your code it's most likely properly formatted.