pptx: Fix list level numbering

In PowerPoint, the content of a top-level list is at the same level as
the content of a top-level paragraph – the only difference is that a
list style has been applied.

At the moment, the pptx writer increments the paragraph level on each
list, turning what should be top-level lists into second-level lists.

This commit changes that logic, only incrementing the paragraph level on
continuation paragraphs of lists.

- Fixes https://github.com/jgm/pandoc/issues/4828
- Fixes https://github.com/jgm/pandoc/issues/4663

3 files changed, 20 insertions, 0 deletions

diff --git a/test/pptx/list-level/input.native b/test/pptx/list-level/input.native
new file mode 100644
index 000000000..e0b36b8e5
--- /dev/null
+++ b/test/pptx/list-level/input.native
@@ -0,0 +1,20 @@
+[Header 1 ("slide",[],[]) [Str "Slide"]
+,BulletList
+ [[Para [Str "Top-level"]
+  ,Para [Str "With",Space,Str "continuation",Space,Str "paragraph"]]
+ ,[Para [Str "Then:"]
+  ,BulletList
+   [[Plain [Str "nested"]]
+   ,[Plain [Str "list"]]
+   ,[Plain [Str "items"]]]]]
+,Header 1 ("slide-1",[],[]) [Str "Slide"]
+,Para [Str "Paragraph."]
+,OrderedList (1,Decimal,Period)
+ [[Para [Str "Top-level"]
+  ,Para [Str "Continuation"]
+  ,OrderedList (1,Decimal,Period)
+   [[Para [Str "Sub-list"]
+    ,Para [Str "With",Space,Str "Continuation"]]
+   ,[Para [Str "(still",Space,Str "sub-list)"]]]]
+ ,[Para [Str "(back",Space,Str "to",Space,Str "top-level)"]]]
+,Para [Str "Paragraph."]]
diff --git a/test/pptx/list-level/output.pptx b/test/pptx/list-level/output.pptx
new file mode 100644
index 000000000..5e3506958
--- /dev/null
+++ b/test/pptx/list-level/output.pptx
diff --git a/test/pptx/list-level/templated.pptx b/test/pptx/list-level/templated.pptx
new file mode 100644
index 000000000..8853a3082
--- /dev/null
+++ b/test/pptx/list-level/templated.pptx