Allow template evaluation in parameters

When passing variables to a sub-task, allow template evaluation
within the passed-on variables.

task.go

@@ -237,7 +237,15 @@ func (e *Executor) runCommand(ctx context.Context, task string, i int, vars Vars
 	cmd := t.Cmds[i]
 
 	if cmd.Cmd == "" {
-		return e.RunTask(ctx, cmd.Task, cmd.Vars)
+		cmdVars := make(Vars, len(cmd.Vars))
+		for k, v := range cmd.Vars {
+			v, err := e.ReplaceVariables(v, task, vars)
+			if err != nil {
+				return err
+			}
+			cmdVars[k] = v
+		}
+		return e.RunTask(ctx, cmd.Task, cmdVars)
 	}
 
 	c, err := e.ReplaceVariables(cmd.Cmd, task, vars)

task_test.go

@@ -178,6 +178,7 @@ func TestParams(t *testing.T) {
 		{"exclamation.txt", "!\n"},
 		{"dep1.txt", "Dependence1\n"},
 		{"dep2.txt", "Dependence2\n"},
+		{"spanish.txt", "¡Holla mundo!\n"},
 	}
 
 	for _, f := range files {

testdata/params/Taskfile.yml

@@ -1,4 +1,6 @@
 default:
+  vars:
+    SPANISH: ¡Holla mundo!
   deps:
     - task: write-file
       vars: {CONTENT: Dependence1, FILE: dep1.txt}
@@ -11,6 +13,8 @@ default:
       vars: {CONTENT: "$echo 'World'", FILE: world.txt}
     - task: write-file
       vars: {CONTENT: "!", FILE: exclamation.txt}
+    - task: write-file
+      vars: {CONTENT: "{{.SPANISH}}", FILE: spanish.txt}
 
 write-file:
   cmds: