Add CONTRIBUTING.md

CONTRIBUTING.md

@@ -0,0 +1,62 @@
+# Contributing Guidelines
+
+We'd love to accept your patches! Please read this guide first.
+
+## Copyright Assignment
+
+Please send an email to Justine Tunney <jtunney@gmail.com> stating that
+you intend to assign her the copyright to the changes you contribute to
+Cosmopolitan. Please use the same email address you use for git commits
+which should only contain original source code from you or other people
+who are also assigning copyright. Please note that, if you're employed,
+you may need to get your employer's approval beforehand. If you can not
+assign copyright due to local laws, then you may alternatively consider
+disclaiming it using the language in [Unlicense](https://unlicense.org)
+or [CC-0](http://creativecommons.org/share-your-work/public-domain/cc0)
+
+This is important because we can't produce 12kb single-file executables
+that comply with license requirements if we have to embed lots of them.
+Although that's less of an issue depending on the purpose of the files.
+For example, ownership is much less of a concern in the unit test files
+so you're encouraged to put your copyright on those, provided it's ISC.
+
+## Style Guide
+
+You can use clang-format to automatically format your files:
+
+```sh
+clang-format -i -style=file tool/net/redbean.c
+```
+
+If you use Emacs this can be automated on save for Cosmopolitan using
+[tool/emacs/cosmo-format.el]([tool/emacs/cosmo-format.el]).
+
+### Source Files
+
+- Must use include paths relative to the root of the repository
+- Must have comment at top of file documenting copyright and license
+- Must have notice embedding if not owned by Justine (exception: tests)
+- May use language extensions that are supported by both GCC and Clang
+- Should use Google indentation (otherwise use `/* clang-format off */`)
+- Should use asm() instead of compiler APIs (exception: ctz, clz, memcpy)
+
+### Header Files
+
+- Must not have copyright or license comments
+- Must have once guards (otherwise change `.h` to `.inc`)
+- Must be ANSI C89 compatible to be included in the amalgamation header
+- Must include its dependencies (exception: libc/integral/normalize.inc)
+- Must not define objects (i.e. `cc -c -xc foo.h` will produce empty `.o`)
+- Should not use typedefs
+- Should not use forward declarations
+- Should not include documentation comments
+- Should not include parameter names in prototypes
+- Should not pose problems if included by C++ or Assembly sources
+- Should not declare non-ANSI code, at all, when the user requests ANSI
+
+### Build Config
+
+- Must not write files outside `o/`
+- Must not communicate with Internet
+- Must not depend on system libraries
+- Must not depend on system commands (exception: sh, make, gzip, zip)