catch2/docs/contributing.md

# Contributing to Catch

So you want to contribute something to Catch? That's great! Whether it's a bug fix, a new feature, support for 
additional compilers - or just a fix to the documentation - all contributions are very welcome and very much appreciated. 
Of course so are bug reports and other comments and questions.

If you are contributing to the code base there are a few simple guidelines to keep in mind. This also includes notes to
help you find your way around. As this is liable to drift out of date please raise an issue or, better still, a pull
request for this file, if you notice that.

## Branches

Ongoing development is currently on _master_. At some point an integration branch will be set-up and PRs should target
 that - but for now it's all against master. You may see feature branches come and go from time to time, too.

## Directory structure

_Users_ of Catch primarily use the single header version. _Maintainers_ should work with the full source (which is still, 
primarily, in headers). This can be found in the `include` folder. There are a set of test files, currently under
`projects/SelfTest`. The test app can be built via CMake from the `CMakeLists.txt` file in the root, or you can generate
project files for Visual Studio, XCode, and others (instructions in the `projects` folder). If you have access to CLion,
it can work with the CMake file directly.

As well as the runtime test files you'll also see a `SurrogateCpps` directory under `projects/SelfTest`.
This contains a set of .cpp files that each `#include` a single header.
While these files are not essential to compilation they help to keep the implementation headers self-contained.
At time of writing this set is not complete but has reasonable coverage.
If you add additional headers please try to remember to add a surrogate cpp for it.

The other directories are `scripts` which contains a set of python scripts to help in testing Catch as well as
generating the single include, and `docs`, which contains the documentation as a set of markdown files.

__When submitting a pull request please do not include changes to the single include, or to the version number file
as these are managed by the scripts!__


## Testing your changes

Obviously all changes to Catch's code should be tested. If you added new functionality, you should add tests covering and
showcasing it. Even if you have only made changes to Catch internals (ie you implemented some performance improvements),
you should still test your changes.

This means 3 things

* Compiling Catch's SelfTest project -- code that does not compile is evidently incorrect. Obviously, you are not expected to
have access to all compilers and platforms Catch supports, Catch's CI pipeline will compile your code using supported compilers
once you open a PR.
* Running the SelfTest binary. There should be no unexpected failures on simple run.
* Running Catch's approval tests. Approval tests compare current output of the SelfTest binary in various configurations against
known good output. Catch's repository provides utility scripts `approvalTests.py` to help you with this. It needs to be passed
the SelfTest binary compiled with your changes, like so: `$ ./scripts/approvalTests.py clang-build/SelfTest`. The output should
be fairly self-explanatory.



 *this document is still in-progress...*

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