Add --shift-heading-level-by option.

Deprecate --base-heading-level.

The new option does everything the old one does, but also
allows negative shifts.  It also promotes the document
metadata (if not null) to a level-1 heading with a +1 shift,
and demotes an initial level-1 heading to document metadata
with a -1 shift. This supports converting documents that
use an initial level-1 heading for the document title.

Closes #5615.

1 files changed, 33 insertions, 0 deletions

diff --git a/test/command/shift-heading-level-by.md b/test/command/shift-heading-level-by.md
new file mode 100644
index 000000000..1d8b8bdd0
--- /dev/null
+++ b/test/command/shift-heading-level-by.md
@@ -0,0 +1,33 @@
+```
+% pandoc --shift-heading-level-by 1 -t native -s
+---
+title: My title
+...
+
+# First heading
+
+## Second
+^D
+Pandoc (Meta {unMeta = fromList []})
+[Header 1 ("",[],[]) [Str "My",Space,Str "title"]
+,Header 2 ("first-heading",[],[]) [Str "First",Space,Str "heading"]
+,Header 3 ("second",[],[]) [Str "Second"]]
+```
+
+```
+% pandoc --shift-heading-level-by -1 -t native -s
+---
+title: Old title
+...
+
+# First heading
+
+## Second
+
+# Another top-level heading
+^D
+Pandoc (Meta {unMeta = fromList [("title",MetaInlines [Str "First",Space,Str "heading"])]})
+[Header 1 ("second",[],[]) [Str "Second"]
+,Para [Str "Another",Space,Str "top-level",Space,Str "heading"]]
+```
+