COMMUNITY.md: update style guide

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

diff --git a/COMMUNITY.md b/COMMUNITY.md
index 8ab6a624ee978978ee55c2a7d96b6b3ed0855698..dfdcf89a172234a422cb41ea6a5b96385a225525 100644 (file)
--- a/COMMUNITY.md
+++ b/COMMUNITY.md
@@ -264,74 +264,74 @@ Portions:
   Copyright (C) 2016 Your name [optional brief change description]
 ```
 
-### Code styling / format
+### Code style / format
 
-Coding style standards in FRR vary depending on location.  Pre-existing
-code uses GNU coding standards.  New code may use Linux kernel coding style.
+FRR uses Linux kernel style except where noted below.
 
-GNU coding style apply to the following parts:
-
-* lib/
-* zebra/
-* bgpd/
-* ospfd/
-* ospf6d/
-* isisd/
-* ripd/
-* ripngd/
-* vtysh/
-
-Linux kernel coding style applies to:
-
-* nhrpd/
-* watchfrr/
-* pimd/
-* lib/{checksum,hook,imsg-buffer,imsg,libfrr,md5,module,monotime,queue}.[ch]
-
-BSD coding style applies to:
-
-* ldpd/
+To help with compliance, in the project root there is a .clang-format
+configuration file which can be used with the `clang-format` tool from the LLVM
+project. In the `tools/` directory there is a Python script named `indent.py`
+that wraps clang-format and handles some edge cases specific to FRR. If you are
+submitting a new file, it is recommended to run that script over the new file
+after ensuring that the latest stable release of `clang-format` is in your
+PATH.
 
 **Whitespace changes in untouched parts of the code are not acceptable in
 patches that change actual code.**  To change/fix formatting issues, please
 create a separate patch that only does formatting changes and nothing else.
 
-It is acceptable to rewrap entire files to Linux kernel style, but this
-**MUST** come as a separate patch that does nothing other than this
-reformatting.
-
+Kernel and BSD styles are documented externally:
 
-#### GNU style
+* [https://www.kernel.org/doc/html/latest/process/coding-style.html](https://www.kernel.org/doc/html/latest/process/coding-style.html)
+* [http://man.openbsd.org/style](http://man.openbsd.org/style)
 
-For GNU coding style, Indentation follows the result of invoking GNU indent:
+For GNU coding style, use `indent` with the following invocation:
 
 ```
 indent -nut -nfc1 file_for_submission.c
 ```
 
-Originally, tabs were used instead of spaces, with tabs are every 8 columns.
-However, tab interoperability issues mean space characters are now preferred for
-new changes. We generally only clean up whitespace when code is unmaintainable
-due to whitespace issues, to minimise merging conflicts.
+#### Exceptions
+
+FRR project code comes from a variety of sources, so there are some stylistic
+exceptions in place. Here they are, by branch.
 
+**For `master`:**
 
-#### Linux kernel & BSD style
+BSD coding style applies to:
 
-These styles are documented externally:
+* ldpd/
 
-* [https://www.kernel.org/doc/Documentation/CodingStyle](https://www.kernel.org/doc/Documentation/CodingStyle).
-* [http://man.openbsd.org/style](http://man.openbsd.org/style)
+`babeld` uses, approximately, the following style:
+
+* K&R style braces
+* Indents are 4 spaces
+* Function return types are on their own line
+
+
+**For `stable/3.0` and `stable/2.0`:**
+
+GNU coding style apply to the following parts:
+
+* lib/
+* zebra/
+* bgpd/
+* ospfd/
+* ospf6d/
+* isisd/
+* ripd/
+* ripngd/
+* vtysh/
 
-They are relatively similar but differ in details.
+BSD coding style applies to:
 
-pimd deviates from Linux kernel style in using 2 spaces for indentation, with
-Tabs replacing 8 spaces, as well as adding a line break between `}` and `else`.
-It is acceptable to convert indentation in pimd/ to Linux kernel style, but
-please convert an entire file at a time.  (Rationale: apart from 2-space
-indentation, the styles are sufficiently close to not upset when mixed.)
+* ldpd/
 
-Unlike GNU style, these styles use tabs, not spaces.
+#### Policy
 
+The above standards relate to code formatting. For other stylistic choices e.g.
+use of `typedef`, variable naming, etc. refer to the Linux kernel style
+documentation.
 
 ### Compile-Time conditional code