add env vars as script vars and prefix with "$".

Author: patinthehat

README.md

@@ -172,10 +172,12 @@ See the [example configuration](./templates/stackup.dist.yaml) for a more comple
 
 Working on a standalone Laravel application? Check out the [example laravel configuration](./templates/stackup.laravel.yaml).
 
-## Available Functions
+## Scripting
+
+Many of the fields in a `Task` can be defined using javascript. To specify an expression to be evaluated, wrap the content in double braces: `{{ env("HOME") }}`.
+
+### Available Functions
 
-Many of the configuration fields can be defined using a javascript expression syntax.
-To specify an expression to be evaluated, wrap the content in double braces: `{{ env("HOME") }}`.
 
 | Function   | Arguments         | Description                                                                 |
 |----------- |------------------ |---------------------------------------------------------------------------- |
@@ -270,6 +272,23 @@ The `SemVer` class is returned by the `semver()` function And is used to parse a
 | `.Patch` | -- | value of the patch version number |
 | `.String` | -- | the original version string |
 
+### Environment Variables
+
+Environment variables can be accessed using the `env()` function or referenced directly as variables by prefixing the variable name with `$` (e.g. `$HOME`).
+
+```yaml
+preconditions:
+    - name: backend project has a docker-compose file
+      check: exists($LOCAL_BACKEND_PROJECT_PATH + "/docker-compose.yml")
+
+tasks:
+  - name: horizon queue
+    id: horizon-queue
+    if: composerJson($LOCAL_BACKEND_PROJECT_PATH + "/composer.json").HasDependency("laravel/horizon");
+    command: php artisan horizon
+    path: '{{ env("LOCAL_BACKEND_PROJECT_PATH") }}'
+    platforms: ['linux', 'darwin']
+```
 ## Dynamic Tasks
 
 You can create dynamic tasks using either the `selectTaskWhen()` or `task()` function:

lib/app/scriptEngine.go

@@ -2,6 +2,7 @@ package app
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	"github.com/robertkrimen/otto"
@@ -33,6 +34,14 @@ func (e *JavaScriptEngine) Init() {
 	CreateScriptAppObject(e.Vm)
 	CreateScriptVarsObject(e.Vm)
 	CreateScriptDevObject(e.Vm)
+	e.CreateEnvironmentVariables()
+}
+
+func (e *JavaScriptEngine) CreateEnvironmentVariables() {
+	for _, env := range os.Environ() {
+		parts := strings.Split(env, "=")
+		e.Vm.Set("$"+parts[0], parts[1])
+	}
 }
 
 func (e *JavaScriptEngine) ToValue(value otto.Value) any {