GitRepo: Add blob lookup method

2 files changed, 65 insertions, 5 deletions

diff --git a/src/buildtool/file_system/git_repo.cpp b/src/buildtool/file_system/git_repo.cpp
index d30f6614..f679647e 100644
--- a/src/buildtool/file_system/git_repo.cpp
+++ b/src/buildtool/file_system/git_repo.cpp
@@ -1313,6 +1313,57 @@ auto GitRepo::CheckTreeExists(std::string const& tree_id,
 #endif  // BOOTSTRAP_BUILD_TOOL
 }
 
+auto GitRepo::CheckBlobExists(std::string const& blob_id,
+                              anon_logger_ptr const& logger) noexcept
+    -> std::optional<bool> {
+#ifdef BOOTSTRAP_BUILD_TOOL
+    return std::nullopt;
+#else
+    try {
+        // preferably with a "fake" repository!
+        if (not IsRepoFake()) {
+            Logger::Log(LogLevel::Debug,
+                        "Blob lookup called on a real repository");
+        }
+        // get git oid
+        git_oid blob_oid;
+        if (git_oid_fromstr(&blob_oid, blob_id.c_str()) != 0) {
+            (*logger)(fmt::format("blob ID parsing in git repository {} failed "
+                                  "with:\n{}",
+                                  GetGitCAS()->git_path_.string(),
+                                  GitLastError()),
+                      true /*fatal*/);
+            return std::nullopt;
+        }
+        // get blob object
+        git_blob* blob_ptr = nullptr;
+        int lookup_res{};
+        {
+            // share the odb lock
+            std::shared_lock lock{GetGitCAS()->mutex_};
+            lookup_res = git_blob_lookup(&blob_ptr, repo_->Ptr(), &blob_oid);
+        }
+        git_blob_free(blob_ptr);
+        if (lookup_res != 0) {
+            if (lookup_res == GIT_ENOTFOUND) {
+                return false;  // blob not found
+            }
+            (*logger)(fmt::format("blob lookup in git repository {} failed "
+                                  "with:\n{}",
+                                  GetGitCAS()->git_path_.string(),
+                                  GitLastError()),
+                      true /*fatal*/);
+            return std::nullopt;
+        }
+        return true;  // blob found
+    } catch (std::exception const& ex) {
+        Logger::Log(
+            LogLevel::Error, "check blob exists failed with:\n{}", ex.what());
+        return std::nullopt;
+    }
+#endif  // BOOTSTRAP_BUILD_TOOL
+}
+
 auto GitRepo::TryReadBlob(std::string const& blob_id,
                           anon_logger_ptr const& logger) noexcept
     -> std::pair<bool, std::optional<std::string>> {
diff --git a/src/buildtool/file_system/git_repo.hpp b/src/buildtool/file_system/git_repo.hpp
index 9c31f21b..05bcfaf3 100644
--- a/src/buildtool/file_system/git_repo.hpp
+++ b/src/buildtool/file_system/git_repo.hpp
@@ -234,12 +234,21 @@ class GitRepo {
         -> std::optional<bool>;
 
     /// \brief Check if given blob ID is present in the directory structure of
-    /// the local repository and try to return it.
+    /// the local repository.
     /// Calling it from a fake repository allows thread-safe use.
-    /// Returns a pair of a success flag, stating that no errors occurred while
-    /// performing the libgit2 calls, and an optional string containing the
-    /// content of the blob, if the blob is found. It guarantees the logger is
-    /// called exactly once with fatal if failure.
+    /// Returns a status of blob presence, or nullopt if failure.
+    /// It guarantees the logger is called exactly once with fatal if failure.
+    [[nodiscard]] auto CheckBlobExists(std::string const& blob_id,
+                                       anon_logger_ptr const& logger) noexcept
+        -> std::optional<bool>;
+
+    /// \brief Check if given blob ID is present in the directory structure
+    /// of the local repository and try to return it. Calling it from a fake
+    /// repository allows thread-safe use. Returns a pair of a success flag,
+    /// stating that no errors occurred while performing the libgit2 calls,
+    /// and an optional string containing the content of the blob, if the
+    /// blob is found. It guarantees the logger is called exactly once with
+    /// fatal if failure.
     [[nodiscard]] auto TryReadBlob(std::string const& blob_id,
                                    anon_logger_ptr const& logger) noexcept
         -> std::pair<bool, std::optional<std::string>>;