Support `configuration variables` (#43)

related to: https://gitea.com/gitea/act_runner/issues/127

This PR make `act` support the expression like `${{ vars.YOUR_CUSTOM_VARIABLES }}`.

Reviewed-on: https://gitea.com/gitea/act/pulls/43
Reviewed-by: Jason Song <i@wolfogre.com>
Co-authored-by: sillyguodong <gedong_1994@163.com>
Co-committed-by: sillyguodong <gedong_1994@163.com>

pkg/exprparser/interpreter.go

@@ -23,6 +23,8 @@ type EvaluationEnvironment struct {
 	Matrix   map[string]interface{}
 	Needs    map[string]Needs
 	Inputs   map[string]interface{}
+
+	Vars map[string]string
 }
 
 type Needs struct {
@@ -181,6 +183,8 @@ func (impl *interperterImpl) evaluateVariable(variableNode *actionlint.VariableN
 		return math.Inf(1), nil
 	case "nan":
 		return math.NaN(), nil
+	case "vars":
+		return impl.env.Vars, nil
 	default:
 		return nil, fmt.Errorf("Unavailable context: %s", variableNode.Name)
 	}

pkg/jobparser/interpeter.go

@@ -62,6 +62,8 @@ func NewInterpeter(
 		Matrix:   matrix,
 		Needs:    using,
 		Inputs:   nil, // not supported yet
+
+		Vars: nil,
 	}
 
 	config := exprparser.Config{

pkg/runner/expression.go

@@ -81,6 +81,8 @@ func (rc *RunContext) NewExpressionEvaluatorWithEnv(ctx context.Context, env map
 		Matrix:   rc.Matrix,
 		Needs:    using,
 		Inputs:   inputs,
+
+		Vars: rc.getVarsContext(),
 	}
 	if rc.JobContainer != nil {
 		ee.Runner = rc.JobContainer.GetRunnerContext(ctx)
@@ -130,6 +132,8 @@ func (rc *RunContext) NewStepExpressionEvaluator(ctx context.Context, step step)
 		// todo: should be unavailable
 		// but required to interpolate/evaluate the inputs in actions/composite
 		Inputs: inputs,
+
+		Vars: rc.getVarsContext(),
 	}
 	if rc.JobContainer != nil {
 		ee.Runner = rc.JobContainer.GetRunnerContext(ctx)

pkg/runner/run_context.go

@@ -683,6 +683,10 @@ func (rc *RunContext) getStepsContext() map[string]*model.StepResult {
 	return rc.StepResults
 }
 
+func (rc *RunContext) getVarsContext() map[string]string {
+	return rc.Config.Vars
+}
+
 func (rc *RunContext) getGithubContext(ctx context.Context) *model.GithubContext {
 	logger := common.Logger(ctx)
 	ghc := &model.GithubContext{

pkg/runner/runner.go

@@ -64,6 +64,7 @@ type Config struct {
 	DefaultActionInstance string                       // the default actions web site
 	PlatformPicker        func(labels []string) string // platform picker, it will take precedence over Platforms if isn't nil
 	JobLoggerLevel        *log.Level                   // the level of job logger
+	Vars                  map[string]string            // the list of variables set at the repository, environment, or organization levels.
 }
 
 func (c Config) GetToken() string {