rust-requirements: allow loading repos with `bookmarksinstore` requirement

`rhg` does support bookmarks, so it can load repos with the
`bookmarksinstore` requirement just as well as other repos.

Differential Revision: https://phab.mercurial-scm.org/D12425

rust/hg-core/src/requirements.rs

@@ -92,6 +92,8 b' const SUPPORTED: &[&str] = &['
     // not should opt out by checking `has_sparse` and `has_narrow`.
     SPARSE_REQUIREMENT,
     NARROW_REQUIREMENT,
+    // rhg doesn't care about bookmarks at all yet
+    BOOKMARKS_IN_STORE_REQUIREMENT,
 ];
 
 // Copied from mercurial/requirements.py:
@@ -103,6 +105,11 b' pub(crate) const DIRSTATE_V2_REQUIREMENT'
 #[allow(unused)]
 pub(crate) const NARROW_REQUIREMENT: &str = "narrowhg-experimental";
 
+/// Bookmarks must be stored in the `store` part of the repository and will be
+/// share accross shares
+#[allow(unused)]
+pub(crate) const BOOKMARKS_IN_STORE_REQUIREMENT: &str = "bookmarksinstore";
+
 /// Enables sparse working directory usage
 #[allow(unused)]
 pub(crate) const SPARSE_REQUIREMENT: &str = "exp-sparse";