Contributing code to Kyua
=========================
Want to contribute? Great! But first, please take a few minutes to read this
document in full. Doing so upfront will minimize the turnaround time required
to get your changes incorporated.
Legal notes
-----------
* Before we can use your code, you must sign the
[Google Individual Contributor License
Agreement](https://developers.google.com/open-source/cla/individual),
also known as the CLA, which you can easily do online. The CLA is necessary
mainly because you own the copyright to your changes, even after your
contribution becomes part of our codebase, so we need your permission to use
and distribute your code. We also need to be sure of various other
things--for instance that you will tell us if you know that your code
infringes on other people's patents. You do not have to sign the CLA until
after you have submitted your code for review and a member has approved it,
but you must do it before we can put your code into our codebase.
* Contributions made by corporations are covered by a different agreement than
the one above: the
[Google Software Grant and Corporate Contributor License
Agreement](https://developers.google.com/open-source/cla/corporate).
Please get your company to sign this agreement instead if your contribution is
on their behalf.
* Unless you have a strong reason not to, please assign copyright of your
changes to Google Inc. and use the 3-clause BSD license text included
throughout the codebase (see [LICENSE](LICENSE)). Keeping the whole project
owned by a single entity is important, particularly to avoid the problem of
having to replicate potentially hundreds of different copyright notes in
documentation materials, etc.
Communication
-------------
* Before you start working on a larger contribution, you should get in touch
with us first through the
[kyua-discuss mailing
list](https://groups.google.com/forum/#!forum/kyua-discuss)
with your idea so that we can help out and possibly guide you. Coordinating
upfront makes it much easier to avoid frustration later on.
* Subscribe to the
[kyua-log mailing list](https://groups.google.com/forum/#!forum/kyua-log) to
get notifications on new commits, Travis CI results, or changes to bugs.
Git workflow
------------
* Always work on a non-master branch.
* Make sure the history of your branch is clean. (Ab)use `git rebase -i master`
to ensure the sequence of commits you want pulled is easy to follow and that
every commit does one (and only one) thing. In particular, commits of the
form `Fix previous` or `Fix build` should never ever exist; merge those fixes
into the relevant commits so that the history is clean at pull time.
* Always trigger Travis CI builds for your changes (hence why working on a
branch is important). Push your branch to GitHub so that Travis CI picks it
up and performs a build. If you have forked the repository, you may need to
enable Travis CI builds on your end. Wait for a green result.
* It is OK and expected for you to `git push --force` on **non-master**
branches. This is required if you need to go through the commit/test cycle
more than once for any given branch after you have "fixed-up" commits to
correct problems spotted in earlier builds.
* Do not send pull requests that subsume other/older pull requests. Each major
change being submitted belongs in a different pull request, which is trivial
to achieve if you use one branch per change as requested in this workflow.
Code reviews
------------
* All changes will be subject to code reviews pre-merge time. In other words:
all pull requests will be carefully inspected before being accepted and they
will be returned to you with comments if there are issues to be fixed.
* Be careful of stylistic errors in your code (see below for style guidelines).
Style violations hinder the review process and distract from the actual code.
By keeping your code clean of style issues upfront, you will speed up the
review process and avoid frustration along the way.
* Whenever you are ready to submit a pull request, review the *combined diff*
you are requesting to be pulled and look for issues. This is the diff that
will be subject to review, not necessarily the individual commits. You can
view this diff in GitHub at the bottom of the `Open a pull request` form that
appears when you click the button to file a pull request, or you can see the
diff by typing `git diff <your-branch> master`.
Commit messages
---------------
* Follow standard Git commit message guidelines. The first line has a maximum
length of 50 characters, does not terminate in a period, and has to summarize
the whole commit. Then a blank line comes, and then multiple plain-text
paragraphs provide details on the commit if necessary with a maximum length of
72-75 characters per line. Vim has syntax highlighting for Git commit
messages and will let you know when you go above the maximum line lengths.
* Use the imperative tense. Say `Add foo-bar` or `Fix baz` instead of `Adding
blah`, `Adds bleh`, or `Added bloh`.
Handling bug tracker issues
---------------------------
* All changes pushed to `master` should cross-reference one or more issues in
the bug tracker. This is particularly important for bug fixes, but also
applies to major feature improvements.
* Unless you have a good reason to do otherwise, name your branch `issue-N`
where `N` is the number of the issue being fixed.
* If the fix to the issue can be done *in a single commit*, terminate the commit
message with `Fixes #N.` where `N` is the number of the issue being fixed and
include a note in `NEWS` about the issue in the same commit. Such fixes can
be merged onto master using fast-forward (the default behavior of `git
merge`).
* If the fix to the issue requires *more than one commit*, do **not** include
`Fixes #N.` in any of the individual commit messages of the branch nor include
any changes to the `NEWS` file in those commits. These "announcement" changes
belong in the merge commit onto `master`, which is done by `git merge --no-ff
--no-commit your-branch`, followed by an edit of `NEWS`, and terminated with a
`git commit -a` with the proper note on the bug being fixed.
Style guide
-----------
These notes are generic and certainly *non-exhaustive*:
* Respect formatting of existing files. Note where braces are placed, number of
blank lines between code chunks, how continuation lines are indented, how
docstrings are typed, etc.
* Indentation is *always* done using spaces, not tabs. The only exception is in
`Makefile`s, where any continuation line within a target must be prefixed by a
*single tab*.
* [Be mindful of spelling and
grammar.](http://julipedia.meroh.net/2013/06/readability-mind-your-typos-and-grammar.html)
Mistakes of this kind are enough of a reason to return a pull request.
* Use proper punctuation for all sentences. Always start with a capital letter
and terminate with a period.
* Respect lexicographical sorting wherever possible.
* Lines must not be over 80 characters.
* No trailing whitespace.
* Two spaces after end-of-sentence periods.
* Two blank lines between functions. If there are two blank lines among code
blocks, they usually exist for a reason: keep them.
* In C++ code, prefix all C identifiers (those coming from `extern "C"`
includes) with `::`.
* Getter functions/methods only need to be documented via `\return`. A
redundant summary is not necessary.