_yaml: Add 'as_bool()' and 'is_none()' to ScalarNode

- 'as_bool()' casts a ScalarNode into a boolean, understanding both
  'True' and 'False' as truthy-falsy values, as per node_get(type=bool)
  behavior
- 'is_none()' allwos checking whether the scalar node contains a 'None'
  value. Since 'None' cannot be used when working with booleans, we need
  to have a way of checking for 'None' when we actually need the
  information of whether the value is unset.
- Adapt all call places to use the new API

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/sources/git.py b/tests/sources/git.py
index 2b8a12997..e3f803469 100644
--- a/tests/sources/git.py
+++ b/tests/sources/git.py
@@ -855,7 +855,7 @@ def test_git_describe(cli, tmpdir, datafiles, ref_storage, tag_type):
             assert 'tag' in tag
             assert 'commit' in tag
             assert 'annotated' in tag
-            assert _yaml.node_get(tag, bool, 'annotated') == (tag_type == 'annotated')
+            assert tag.get_bool('annotated') == (tag_type == 'annotated')
 
         assert {(tag.get_str('tag'),
                  tag.get_str('commit'))
@@ -970,7 +970,7 @@ def test_git_describe_head_is_tagged(cli, tmpdir, datafiles, ref_storage, tag_ty
         assert 'tag' in tag
         assert 'commit' in tag
         assert 'annotated' in tag
-        assert _yaml.node_get(tag, bool, 'annotated') == (tag_type == 'annotated')
+        assert tag.get_bool('annotated') == (tag_type == 'annotated')
 
         tag_name = tag.get_str('tag')
         commit = tag.get_str('commit')