upgrade: Minor tweaks

rust/src/sysroot_upgrade.rs

@@ -189,6 +189,7 @@ pub(crate) fn purge_refspec(repo: &crate::FFIOstreeRepo, imgref: &str) -> CxxRes
     Ok(())
 }
 
+/// Check for an updated manifest for the given container image reference, and return a diff.
 pub(crate) fn compare_local_to_remote_container(
     repo: &crate::FFIOstreeRepo,
     cancellable: &crate::FFIGCancellable,
@@ -199,15 +200,16 @@ pub(crate) fn compare_local_to_remote_container(
     let imgref = &OstreeImageReference::try_from(imgref)?;
     let r = Handle::current().block_on(async {
         crate::utils::run_with_cancellable(
-            async { get_container_manifest_diff(repo, imgref).await },
+            async { impl_get_container_manifest_diff(repo, imgref).await },
             &cancellable,
         )
         .await
     })?;
     Ok(Box::new(r))
 }
 
-pub async fn get_container_manifest_diff(
+/// Implementation of fetching a container manifest diff.
+async fn impl_get_container_manifest_diff(
     repo: &ostree::Repo,
     imgref: &OstreeImageReference,
 ) -> Result<ExportedManifestDiff> {