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 `::`.