Fix the root-level redirect not being generated in cases where there …

…are no versioned books and no book exists for the default branch

CHANGELOG.md

@@ -15,6 +15,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
 
 * A GitHub link is now added to the navbar by default (fixes [#26](https://github.com/hexdoc-dev/hexdoc/issues/26)). See the [docs](https://hexdoc.hexxy.media/docs/guides/template/#navbar) for more info.
 
+### Fixed
+
+* Fix the root-level redirect not being generated in cases where there are no versioned books and no book exists for the default branch.
+
 ## `1!0.1.0a19`
 
 ### Added

src/hexdoc/cli/app.py

@@ -365,8 +365,17 @@ def merge(
 
     if root_redirect is None:
         # TODO: use plugin to build this path
+        # TODO: refactor
         if item := sitemap.get(f"latest/{props.default_branch}"):
             root_redirect = item.default_marker.redirect_contents
+        elif sitemap:
+            key = sorted(sitemap.keys())[0]
+            root_redirect = sitemap[key].default_marker.redirect_contents
+            logger.warning(
+                f"No book exists for the default branch `{props.default_branch}`, generating root redirect to `{key}` (check the value of `default_branch` in hexdoc.toml)"
+            )
+        else:
+            logger.error("No books found, skipping root redirect")
 
     if root_redirect is not None:
         redirects[Path()] = root_redirect