Add duplicate command groups test source file

tbidne · tbidne · commit 0e0e43ae6f92 · 2024-07-22T21:45:57.000+12:00
diff --git a/optparse-applicative.cabal b/optparse-applicative.cabal
@@ -42,6 +42,7 @@ extra-source-files:  CHANGELOG.md
                      tests/parser_group_all_grouped.err.txt
                      tests/parser_group_basic.err.txt
                      tests/parser_group_command_groups.err.txt
+                     tests/parser_group_duplicate_command_groups.err.txt
                      tests/parser_group_duplicates.err.txt
                      tests/parser_group_nested.err.txt
                      tests/nested_optional.err.txt
