Issue #3495143 by phenaproxima, poker10, pameeela: Document that Package...

Issue #3495143 by phenaproxima, poker10, pameeela: Document that Package Manager cannot be used in DDEV with the development repo

README.md

-# Drupal CMS
+# Drupal CMS development repository
 
-**WARNING:** This repository is only for contributing to Drupal CMS. Do not use it to build sites.
+**WARNING:** This repository is only for contributing to Drupal CMS. Do not use it to build sites. If you want to give Drupal CMS a try, [visit its project page](https://www.drupal.org/project/cms).
 
-If you want to give Drupal CMS a try, don't use this repository. Instead, do the following:
+## Getting Started
+To contribute to Drupal CMS, you'll need [DDEV](https://ddev.com/), which is our officially supported platform for contribution. [Install it on your machine](https://ddev.com/get-started), then follow these instructions:
 
-1. Install [DDEV](https://ddev.com/) according to [its documentation](https://ddev.readthedocs.io/en/stable/).
-2. Download and unzip [Drupal CMS's most recent release](https://www.drupal.org/project/cms/releases).
-3. In the unzipped directory, run `./launch-drupal-cms.sh` at the command line.
+1. Follow the instructions to clone this repository.
+2. At the command line, go into the repository root and run `ddev launch`.
 
-That's it! DDEV will automatically configure everything and open Drupal CMS in your default browser.
+## Code of Conduct
+Drupal CMS has adopted a [code of conduct](https://www.drupal.org/dcoc) that we expect all participants to adhere to.
+
+## Getting Help
+Find us in [the #drupal-cms-development channel](https://drupal.slack.com/archives/C072BF486FN) in Drupal Slack.
+
+## Known Issues
+* You cannot use Project Browser (or any module based on the core Package Manager module) to install new extensions into the DDEV project. You _can_ install extensions (or apply recipes) that are already present, though.
+
+## Useful Commands
+
+### Applying a Recipe
+```shell
+ddev drush recipe ../recipes/NAME_OF_RECIPE
+```
+### Running Tests
+Once the project's containers are up and running (run `ddev start` to ensure that), you can use the following commands to run Drupal CMS's tests.
+
+Run all tests, in all recipes:
+```shell
+ddev test
+```
+Run all tests in a single recipe:
+```shell
+ddev test recipes/NAME_OF_RECIPE
+```
+Run all end-to-end (Cypress) tests, in all recipes:
+```shell
+ddev npm test
+```
+Run all end-to-end tests in a single recipe:
+```shell
+ddev npm test -- --spec="recipes/NAME_OF_RECIPE/tests/e2e/*.cy.js"
+```
+Run all PHPUnit tests in a single recipe:
+```shell
+ddev exec phpunit -c web/core recipes/NAME_OF_RECIPE
+```
+Run a single PHPUnit test:
+```shell
+ddev exec phpunit -c web/core path/to/test/file.php
+```
+Run Cypress with custom options.
+```shell
+ddev npm test -- CUSTOM_OPTIONS...
+```
+Run PHPUnit with custom options.
+```shell
+ddev exec phpunit CUSTOM_OPTIONS...
+```
+
+### Reinstalling Drupal CMS
+Reinstall with the currently installed dependencies:
+```shell
+ddev drush site:install --yes
+```
+Reinstall via the UI, with the currently installed dependencies:
+```shell
+ddev drush sql:drop --yes && ddev launch
+```
+Delete and reinstall all dependencies:
+```shell
+ddev exec rm -r -f vendor web composer.lock && ddev restart
+```