provisioner/shell: execute script directly instead of using /bin/sh

provisioner/shell/provisioner.go

@@ -62,7 +62,7 @@ func (p *Provisioner) Prepare(raws ...interface{}) error {
 	}
 
 	if p.config.ExecuteCommand == "" {
-		p.config.ExecuteCommand = "{{.Vars}} sh {{.Path}}"
+		p.config.ExecuteCommand = "chmod +x {{.Path}}; {{.Vars}} {{.Path}}"
 	}
 
 	if p.config.Inline != nil && len(p.config.Inline) == 0 {

website/source/docs/provisioners/shell.html.markdown

@@ -51,7 +51,7 @@ Optional parameters:
   `key=value`.
 
 * `execute_command` (string) - The command to use to execute the script.
-  By default this is `{{ .Vars }} sh {{ .Path }}`. The value of this is
+  By default this is `chmod +x {{ .Path }}; {{ .Vars }} {{ .Path }}`. The value of this is
   treated as [configuration template](/docs/templates/configuration-
   templates.html). There are two available variables: `Path`, which is
   the path to the script to run, and `Vars`, which is the list of