Document installation methods

CONTRIBUTING.md

@@ -11,3 +11,156 @@ Please note we have a [code of conduct](CODE_OF_CONDUCT.md). Please follow it in
 * Provide good commit messages describing what you've done.
 * Provide tests for any code you write.
 * Make sure all tests are passing.
+* Prefer `phar` downloads or `composer-bin-plugin` installation over `composer global` installations to avoid dependency conflicts.
+* Update the `tools.json` with any new tools'd like to add.
+* Update `README.md` with any new tools you added (`php bin/devkit.php update:readme`).
+
+## Adding a new tool
+
+To add support for a new tool, add it to the list in `resources/tools.json`:
+
+```json
+{
+  "name": "behat",
+  "summary": "Helps to test business expectations",
+  "website": "http://behat.org/",
+  "command": {
+    "composer-bin-plugin": {
+      "package": "behat/behat",
+      "namespace": "behat"
+    }
+  },
+  "test": "behat --version"
+}
+```
+
+Each tool should have the following properties specified:
+
+* `name` - name of the tool, most of the time the name of executable;
+* `summary` - shortly stated purpose of the tool;
+* `website` - link to the tool's website;
+* `command` - the command to install the tool. See supported commands below;
+* `test` - the command to verify if the tool is installed. Most of the time it will be the command to show the version or help;
+
+Once you added a new tool to the list, update the list in `README.md` by running the following command:
+
+```bash
+php bin/toolsbox update:readme
+```
+
+### Commands
+
+There are several supported ways to install tools.
+All of them are listed below in order of preference.
+
+#### composer-bin-plugin
+
+The `composer-bin-plugin` method uses the [bamarni/composer-bin-plugin](https://github.com/bamarni/composer-bin-plugin)
+to install the package in isolated directory.
+Thanks to the isolation we're less likely to run into problem with conflicting dependencies between tools.
+
+```json
+{
+  "command": {
+    "composer-bin-plugin": {
+      "package": "behat/behat",
+      "namespace": "behat"
+    }
+  }
+}
+```
+
+#### phar-download
+
+Downloads a phar from the given URL and puts it into the specified location.
+
+```json
+{
+  "command": {
+    "phar-download": {
+      "phar": "https://github.com/phpspec/phpspec/releases/download/4.3.0/phpspec.phar",
+      "bin": "/usr/local/bin/phpspec"
+    }
+  }
+}
+```
+
+#### file-download
+
+Downloads a file from the given URL and puts it into the specified location.
+
+```json
+{
+  "command": {
+    "file-download": {
+      "url": "https://github.com/vimeo/psalm/releases/download/2.0.0/psalm.phar.asc",
+      "file": "/usr/local/bin/psalm.phar.asc"
+    }
+  }
+}
+```
+
+#### box-build
+
+Uses [box](https://box-project.github.io/box2/) to build a phar and puts it into the specified location.
+It will clone the given repository and checkout the latest tag if available.
+
+```json
+{
+  "command": {
+    "box-build": {
+      "repository": "https://github.com/behat/behat.git",
+      "phar": "behat.phar",
+      "bin": "/usr/local/bin/behat"
+    }
+  }
+}
+```
+
+#### composer-global-install
+
+Uses the `composer global require` command to install a composer package globally.
+
+```json
+{
+  "command": {
+    "composer-global-install": {
+      "package": "bmitch/churn-php"
+    }
+  }
+}
+```
+
+#### composer-install
+
+Clones the specified repository, checkouts the latest tag (if available), and runs `composer install` inside.
+Mostly useful with applications.
+
+```json
+{
+  "command": {
+    "composer-install": {
+      "repository": "https://github.com/Qafoo/QualityAnalyzer.git"
+    }
+  }
+}
+```
+
+#### Executing multiple commands
+
+It's sometimes useful to run multiple installation commands i.e. when downloading a phar and its signature.
+
+```json
+{
+  "command": {
+    "file-download": {
+      "url": "https://github.com/vimeo/psalm/releases/download/2.0.0/psalm.phar.asc",
+      "file": "/usr/local/bin/psalm.phar.asc"
+    },
+    "phar-download": {
+      "phar": "https://github.com/vimeo/psalm/releases/download/2.0.0/psalm.phar",
+      "bin": "/usr/local/bin/psalm"
+    }
+  }
+}
+```