Fix setting rebuild condition

Sphinx clarifies that this should be a literal type not, not a boolean
in general.

changelog.d/20240430_155714_jsick_DM_44137.md

@@ -4,6 +4,8 @@
 
 - In `documenteer.ext.lssttasks`, attempt to import `_pseudo_parse_arglist` from `sphinx.domains.python._annotations` before falling back to the `sphinx.domains.python` module. Ultimately this is a workaround.
 
+- Fix setting the rebuild condition for the `documenteer.ext.githubbibcache` extension.
+
 ### Other changes
 
 - Added `defusedxml` as a dev dependency. This is used by Sphinx's `sphinx.testing.fixtures`, but isn't included as a dependency by Sphinx itself. This change ensures that `defusedxml` is installed when running the tests.

src/documenteer/ext/githubbibcache.py

@@ -116,11 +116,11 @@ def cache_bibfiles(app: Sphinx, config: Config) -> None:
 def setup(app: Sphinx) -> dict[str, Any]:
     """Set up the ``documenteer.ext.autocppapi`` Sphinx extensions."""
     # Configuration values
-    app.add_config_value("documenteer_bibfile_github_repos", "", True, [list])
+    app.add_config_value("documenteer_bibfile_github_repos", "", "env", [list])
     app.add_config_value(
         "documenteer_bibfile_cache_dir",
         Path("_build/bibfile-cache"),
-        True,
+        "env",
         [str, Path],
     )
     app.connect("config-inited", cache_bibfiles)