improve CONTRIBUTING.md and add rules for PRs

1 files changed, 43 insertions, 63 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 56bb4b6eb9..e9c5fe2014 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,74 +1,54 @@
 # How to contribute
 
-We definitely welcome patches and contribution to grpc! Here is some guideline
-and information about how to do so.
+We definitely welcome your patches and contributions to gRPC!
 
-## Getting started
+If you are new to github, please start by reading [Pull Request howto](https://help.github.com/articles/about-pull-requests/)
 
-### Legal requirements
+## Legal requirements
 
 In order to protect both you and ourselves, you will need to sign the
 [Contributor License Agreement](https://cla.developers.google.com/clas).
 
-### Technical requirements
+## Running tests
+
+Use `tools/run_tests/run_tests.py` script to run the unit tests.
+See [tools/run_tests](tools/run_tests) for how to run tests for a given language.
+
+Prerequisites for building and running tests are listed in [INSTALL.md](INSTALL.md)
+and in `src/YOUR-LANGUAGE` (e.g. `src/csharp`)
+
+## Generated project files
+
+To ease maintenance of language- and platform- specific build systems,
+many projects files are generated using templates and should not be edited
+by hand.
+Run `tools/buildgen/generate_projects.sh` to regenerate.
+See [templates](templates) for details.
+
+As a rule of thumb, if you see the "sanity tests" failing you've most likely edited generated files or you didn't regenerate the projects properly (or your code formatting doesn't match our code style).
+
+## Guidelines for Pull Requests
+How to get your contributions merged smoothly and quickly.
+ 
+- Create **small PRs** that are narrowly focused on **addressing a single concern**. We often times receive PRs that are trying to fix several things at a time, but only one fix is considered acceptable, nothing gets merged and both author's & review's time is wasted. Create more PRs to address different concerns and everyone will be happy.
+ 
+- For speculative changes, consider opening an issue and discussing it first. If you are suggesting a behavioral or API change, consider starting with a [gRFC proposal](https://github.com/grpc/proposal). 
+ 
+- Provide a good **PR description** as a record of **what** change is being made and **why** it was made. Link to a github issue if it exists.
+ 
+- Don't fix code style and formatting unless you are already changing that line to address an issue. PRs with irrelevant changes won't be merged. If you do want to fix formatting or style, do that in a separate PR.
+ 
+- Unless your PR is trivial, you should expect there will be reviewer comments that you'll need to address before merging. We expect you to be reasonably responsive to those comments, otherwise the PR will be closed after 2-3 weeks of inactivity.
+ 
+- Maintain **clean commit history** and use **meaningful commit messages**. PRs with messy commit history are difficult to review and won't be merged. Use `rebase -i upstream/master` to curate your commit history and/or to bring in latest changes from master (but avoid rebasing in the middle of a code review).
+ 
+- Keep your PR up to date with upstream/master (if there are merge conflicts, we can't really merge your change).
+ 
+- if you are regenerating the projects using `tools/buildgen/generate_projects.sh`, make changes to generated files a separate commit with commit message `regenerate projects`. Mixing changes to generated and hand-written files make your PR difficult to review.
+ 
+- **All tests need to be passing** before your change can be merged. We recommend you **run tests locally** before creating your PR to catch breakages early on (see [tools/run_tests](tools/run_tests). Ultimately, the green signal will be provided by our testing infrastructure. The reviewer will help you if there are test failures that seem not related to the change you are making.
+ 
+- Exceptions to the rules can be made if there's a compelling reason for doing so.
 
-You will need several tools to work with this repository. In addition to all of
-the packages described in the [INSTALL](INSTALL.md) file, you will also need
-python, and the mako template renderer. To install the latter, using pip, one
-should simply be able to do `pip install mako`.
 
-In order to run all of the tests we provide, you will need valgrind and clang.
-More specifically, under debian, you will need the package libc++-dev to
-properly run all the tests.
 
-Compiling and running grpc C++ tests depend on protobuf 3.0.0, gtest and gflags.
-Although gflags is provided in third_party, you will need to manually install
-that dependency on your system to run these tests. Under a Debian or Ubuntu
-system, you can install the gtests and gflags packages using apt-get:
-
-```sh
- $ [sudo] apt-get install libgflags-dev libgtest-dev
-```
-
-If you are planning to work on any of the languages other than C and C++, you
-will also need their appropriate development environments.
-
-If you want to work under Windows, we recommend the use of Visual Studio 2013.
-The [Community or Express editions](http://www.visualstudio.com/en-us/downloads/download-visual-studio-vs.aspx)
-are free and suitable for developing with grpc. Note however that our test
-environment and tools are available for Unix environments only at the moment.
-
-## Testing your changes
-
-We provide a tool to help run the suite of tests in various environments.
-In order to run most of the available tests, one would need to run:
-
-`./tools/run_tests/run_tests.py`
-
-If you want to run tests for any of the languages {c, c++, csharp, node, objc, php, python, ruby}, do this:
-
-`./tools/run_tests/run_tests.py -l <lang>`
-
-To know about the list of available commands, do this:
-
-`./tools/run_tests/run_tests.py -h`
-
-If you are running tests for ObjC on osx, follow these steps before running tests:
-* install Xcode command-line tools by running
-`sudo xcode-select --install`
-* install macports from https://www.macports.org/install.php
-* install autoconf, automake, libtool, gflags, cmake using macports
-* restart your terminal window or run source ~/.bash_profile to pick up the new PATH changes.
-
-## Adding or removing source code
-
-Each language uses its own build system to work. Currently, the root's Makefile
-and the Visual Studio project files are building only the C and C++ source code.
-In order to ease the maintenance of these files, we have a
-template system. Please do not contribute manual changes to any of the generated
-files. Instead, modify the template files, or the build.yaml file, and
-re-generate the project files using the following command:
-
-`./tools/buildgen/generate_projects.sh`
-
-You'll find more information about this in the [templates](templates) folder.