StorageUtils: Add generation-aware rehashing ID file map

Such a file could be used to store mappings of digests from CAS or
Git cache to digests of different hash type that represent same
content.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/buildtool/storage/fs_utils.cpp b/src/buildtool/storage/fs_utils.cpp
index 171a5d1c..05883814 100644
--- a/src/buildtool/storage/fs_utils.cpp
+++ b/src/buildtool/storage/fs_utils.cpp
@@ -104,6 +104,16 @@ auto GetResolvedTreeIDFile(StorageConfig const& storage_config,
            tree_hash;
 }
 
+auto GetRehashIDFile(StorageConfig const& storage_config,
+                     HashFunction::Type target_hash_type,
+                     std::string const& hash,
+                     bool from_git,
+                     std::size_t generation) noexcept -> std::filesystem::path {
+    return storage_config.GenerationCacheRoot(generation) /
+           fmt::format("to-{}", ToString(target_hash_type)) /
+           (from_git ? "from-git" : "from-cas") / hash;
+}
+
 auto WriteTreeIDFile(std::filesystem::path const& tree_id_file,
                      std::string const& tree_id) noexcept -> bool {
     // needs to be done safely, so use the rename trick