1 files changed, 6 insertions, 0 deletions
diff --git a/src/buildtool/file_system/git_cas.hpp b/src/buildtool/file_system/git_cas.hpp
index 44b61cb4..f95cb403 100644
--- a/src/buildtool/file_system/git_cas.hpp
+++ b/src/buildtool/file_system/git_cas.hpp
@@ -18,6 +18,7 @@
 #include <filesystem>
 #include <memory>
 #include <optional>
+#include <shared_mutex>
 #include <unordered_map>
 #include <vector>
 
@@ -67,6 +68,11 @@ class GitCAS {
     // git folder path of repo
     std::filesystem::path git_path_{};
 
+    // mutex to guard odb while setting up a "fake" repository; it needs to be
+    // uniquely owned while wrapping the odb, but then git operations are free
+    // to share it.
+    mutable std::shared_mutex mutex_{};
+
     [[nodiscard]] auto OpenODB(std::filesystem::path const& repo_path) noexcept
         -> bool;