feat: allow to spawn and run a local reusable workflow (#1423)

* feat: allow to spawn and run a local reusable workflow

This change contains the ability to parse/plan/run a local
reusable workflow.
There are still numerous things missing:

- inputs
- secrets
- outputs

* feat: add workflow_call inputs

* test: improve inputs test

* feat: add input defaults

* feat: allow expressions in inputs

* feat: use context specific expression evaluator

* refactor: prepare for better re-usability

* feat: add secrets for reusable workflows

* test: use secrets during test run

* feat: handle reusable workflow outputs

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

act/runner/reusable_workflow.go

@@ -0,0 +1,45 @@
+package runner
+
+import (
+	"fmt"
+	"path"
+
+	"github.com/nektos/act/pkg/common"
+	"github.com/nektos/act/pkg/model"
+)
+
+func newLocalReusableWorkflowExecutor(rc *RunContext) common.Executor {
+	return newReusableWorkflowExecutor(rc, rc.Config.Workdir)
+}
+
+func newRemoteReusableWorkflowExecutor(rc *RunContext) common.Executor {
+	return common.NewErrorExecutor(fmt.Errorf("remote reusable workflows are currently not supported (see https://github.com/nektos/act/issues/826 for updates)"))
+}
+
+func newReusableWorkflowExecutor(rc *RunContext, directory string) common.Executor {
+	planner, err := model.NewWorkflowPlanner(path.Join(directory, rc.Run.Job().Uses), true)
+	if err != nil {
+		return common.NewErrorExecutor(err)
+	}
+
+	plan := planner.PlanEvent("workflow_call")
+
+	runner, err := NewReusableWorkflowRunner(rc)
+	if err != nil {
+		return common.NewErrorExecutor(err)
+	}
+
+	return runner.NewPlanExecutor(plan)
+}
+
+func NewReusableWorkflowRunner(rc *RunContext) (Runner, error) {
+	runner := &runnerImpl{
+		config:    rc.Config,
+		eventJSON: rc.EventJSON,
+		caller: &caller{
+			runContext: rc,
+		},
+	}
+
+	return runner.configure()
+}