Fix bug in includes where default taskfiles were not being checked.

testdata/includes_multi_level/Taskfile.yml

@@ -1,9 +1,11 @@
 version: '3'
 
 includes:
-  'one': ./one/Taskfile.yml
+  'one': ./one/
 
 tasks:
   default:
     cmds:
+      - task: one:default
       - task: one:two:default
+      - task: one:two:three:default

testdata/includes_multi_level/called_one.txt

@@ -0,0 +1 @@
+one

testdata/includes_multi_level/called_three.txt

@@ -0,0 +1 @@
+three

testdata/includes_multi_level/called_two.txt

@@ -0,0 +1 @@
+two

testdata/includes_multi_level/one/Taskfile.yml

@@ -1,9 +1,7 @@
 version: '3'
 
 includes:
-  'two': ./two/Taskfile.yml
+  'two': ./two/
 
 tasks:
-  level1:
-    cmds:
-      - echo "hello level 1"
+  default: echo one > called_one.txt

testdata/includes_multi_level/one/two/Taskfile.yml

@@ -1,6 +1,7 @@
 version: '3'
 
+includes:
+  'three': ./three/Taskfile.yml
+
 tasks:
-  default:
-    cmds:
-      - echo "called_dep" > called_dep.txt
+  default: echo two > called_two.txt

testdata/includes_multi_level/one/two/three/Taskfile.yml

@@ -0,0 +1,4 @@
+version: '3'
+
+tasks:
+  default: echo three > called_three.txt