Script mode set -xe by default when no shebang used

docs/tasks.md

@@ -156,11 +156,16 @@ If this field is present, the step cannot specify `command`.
 When specified, a `script` gets invoked as if it were the contents of a file in
 the container. Any `args` are passed to the script file.
 
-Scripts that do not start with a shebang
-[shebang](https://en.wikipedia.org/wiki/Shebang_(Unix)) line will use a default
-value of `#!/bin/sh`, although users can override this by starting their script
-with a shebang to declare what tool should be used to interpret the script.
-That tool must then also be available within the step's container.
+Scripts that do not start with a [shebang](https://en.wikipedia.org/wiki/Shebang_(Unix))
+line will use the following default preamble:
+
+```bash
+#!/bin/sh
+set -xe
+```
+Users can override this by starting their script with a shebang to declare what
+tool should be used to interpret the script. That tool must then also be
+available within the step's container.
 
 This allows you to execute a Bash script, if the image includes `bash`:
 

pkg/pod/script.go

@@ -27,9 +27,9 @@ import (
 )
 
 const (
-	scriptsVolumeName = "scripts"
-	scriptsDir        = "/tekton/scripts"
-	defaultShebang    = "#!/bin/sh\n"
+	scriptsVolumeName     = "scripts"
+	scriptsDir            = "/tekton/scripts"
+	defaultScriptPreamble = "#!/bin/sh\nset -xe\n"
 )
 
 var (
@@ -77,7 +77,7 @@ func convertScripts(shellImage string, steps []v1alpha1.Step) (*corev1.Container
 
 		script := s.Script
 		if !hasShebang {
-			script = defaultShebang + s.Script
+			script = defaultScriptPreamble + s.Script
 		}
 
 		// At least one step uses a script, so we should return a

pkg/pod/script_test.go

@@ -101,6 +101,7 @@ tmpfile="/tekton/scripts/script-3-j2tds"
 touch ${tmpfile} && chmod +x ${tmpfile}
 cat > ${tmpfile} << 'script-heredoc-randomly-generated-vr6ds'
 #!/bin/sh
+set -xe
 no-shebang
 script-heredoc-randomly-generated-vr6ds
 `},