manifest: add shallow option to treemanifestctx.readdelta and readfast...
manifest: add shallow option to treemanifestctx.readdelta and readfast
The old manifest had different functions for performing shallow reads, shallow
readdeltas, and shallow readfasts. Since a lot of the code is duplicate (and
since those functions don't make sense on a normal manifestctx), let's unify
them into flags on the existing readdelta and readfast functions.
A future diff will change consumers of these functions to use the manifestctx
versions and will delete the old apis.