Updated README

Author: Alexey Inkin

README.md

@@ -6,29 +6,59 @@
 
 ---
 
-This repository (`phpstan/phpstan-src`) is for PHPStan's development only. Head to [`phpstan/phpstan`](https://github.com/phpstan/phpstan) for the main README, or to [create an issue](https://github.com/phpstan/phpstan/issues/new/choose). 
-
-## Code of Conduct
-
-This project adheres to a [Contributor Code of Conduct](https://github.com/phpstan/phpstan/blob/master/CODE_OF_CONDUCT.md).
-By participating in this project and its community, you are expected to uphold this code.
+This repository (`phpstan/phpstan-src`) is for PHPStan's development only. Head to [`phpstan/phpstan`](https://github.com/phpstan/phpstan) for the main README, or to [create an issue](https://github.com/phpstan/phpstan/issues/new/choose).
 
 ## Contributing
 
 Any contributions are welcome.
 
 ### Building
 
-Initially you need to run `composer install`, or `composer update` in case you aren't working in a folder which was built before.
+Initially you need to run `composer install`, or `composer update` in case you aren't working in a directory which was built before.
 
 Afterwards you can either run the whole build including linting and coding standards using
 
 ```bash
 vendor/bin/phing
 ```
 
-or run only tests using
+### Running development version
+
+You can also choose to run only part of the build. To analyse PHPStan by PHPStan itself, run:
+
+```bash
+vendor/bin/phing phpstan
+```
+
+### Fixing code style
+
+To detect code style issues, run:
 
+```bash
+vendor/bin/phing cs
+```
+
+This requires PHP 7.4. On older versions the build target will be skipped and succeed silently.
+
+And then to fix code style, run:
+
+```bash
+vendor/bin/phing cs-fix
+```
+
+### Running tests
+
+Run:
 ```bash
 vendor/bin/phing tests
 ```
+
+### Debugging
+
+1. Make sure XDebug is installed and configured.
+2. Add `--xdebug` option when running PHPStan. Without it PHPStan turns the debugger off at runtime.
+
+## Code of Conduct
+
+This project adheres to a [Contributor Code of Conduct](https://github.com/phpstan/phpstan/blob/master/CODE_OF_CONDUCT.md).
+By participating in this project and its community, you are expected to uphold this code.