bug/issue #2448 - manage special bash options when no shell is defined (#2449)

* bash without "-o pipefail" option when "bash" is not explicitely
defined in the workflow
* bonus: fix inverted expected and actual in TestGetGitHubContext assertions

pkg/model/workflow.go

@@ -572,6 +572,8 @@ type Step struct {
 	Uses               string            `yaml:"uses"`
 	Run                string            `yaml:"run"`
 	WorkingDirectory   string            `yaml:"working-directory"`
+	// WorkflowShell is the shell really configured in the job, directly at step level or higher in defaults.run.shell
+	WorkflowShell      string            `yaml:"-"`
 	Shell              string            `yaml:"shell"`
 	Env                yaml.Node         `yaml:"env"`
 	With               map[string]string `yaml:"with"`
@@ -614,8 +616,14 @@ func (s *Step) ShellCommand() string {
 
 	//Reference: https://github.com/actions/runner/blob/8109c962f09d9acc473d92c595ff43afceddb347/src/Runner.Worker/Handlers/ScriptHandlerHelpers.cs#L9-L17
 	switch s.Shell {
-	case "", "bash":
-		shellCommand = "bash --noprofile --norc -e -o pipefail {0}"
+	case "":
+		shellCommand = "bash -e {0}"
+	case "bash":
+		if s.WorkflowShell == "" {
+			shellCommand = "bash -e {0}"
+		} else {
+			shellCommand = "bash --noprofile --norc -e -o pipefail {0}"
+		}
 	case "pwsh":
 		shellCommand = "pwsh -command . '{0}'"
 	case "python":