git_repo: Add blob writer method

Also extends the tests accordingly.

2 files changed, 41 insertions, 0 deletions

diff --git a/src/buildtool/file_system/git_repo.cpp b/src/buildtool/file_system/git_repo.cpp
index c0774971..c7ecddda 100644
--- a/src/buildtool/file_system/git_repo.cpp
+++ b/src/buildtool/file_system/git_repo.cpp
@@ -1433,6 +1433,38 @@ auto GitRepo::TryReadBlob(std::string const& blob_id,
 #endif  // BOOTSTRAP_BUILD_TOOL
 }
 
+auto GitRepo::WriteBlob(std::string const& content,
+                        anon_logger_ptr const& logger) noexcept
+    -> std::optional<std::string> {
+#ifdef BOOTSTRAP_BUILD_TOOL
+    return std::nullopt;
+#else
+    try {
+        // preferably with a "fake" repository!
+        if (not IsRepoFake()) {
+            Logger::Log(LogLevel::Debug,
+                        "Blob writer called on a real repository");
+        }
+        // share the odb lock
+        std::shared_lock lock{GetGitCAS()->mutex_};
+
+        git_oid blob_oid;
+        if (git_blob_create_from_buffer(
+                &blob_oid, repo_->Ptr(), content.c_str(), content.size()) !=
+            0) {
+            (*logger)(fmt::format("writing blob into database failed with:\n{}",
+                                  GitLastError()),
+                      /*fatal=*/true);
+            return std::nullopt;
+        }
+        return std::string{git_oid_tostr_s(&blob_oid)};
+    } catch (std::exception const& ex) {
+        Logger::Log(LogLevel::Error, "write blob failed with:\n{}", ex.what());
+        return std::nullopt;
+    }
+#endif  // BOOTSTRAP_BUILD_TOOL
+}
+
 auto GitRepo::GetObjectByPathFromTree(std::string const& tree_id,
                                       std::string const& rel_path) noexcept
     -> std::optional<TreeEntryInfo> {
diff --git a/src/buildtool/file_system/git_repo.hpp b/src/buildtool/file_system/git_repo.hpp
index 885ddde1..60353a00 100644
--- a/src/buildtool/file_system/git_repo.hpp
+++ b/src/buildtool/file_system/git_repo.hpp
@@ -263,6 +263,15 @@ class GitRepo {
                                    anon_logger_ptr const& logger) noexcept
         -> std::pair<bool, std::optional<std::string>>;
 
+    /// \brief Write given content as a blob into underlying object database.
+    /// Calling it from a fake repository allows thread-safe use.
+    /// \returns Git ID of the written blob, or nullopt on errors.
+    /// It guarantees the logger is called exactly once with fatal if failure.
+    /// Use with care, especially for large objects.
+    [[nodiscard]] auto WriteBlob(std::string const& content,
+                                 anon_logger_ptr const& logger) noexcept
+        -> std::optional<std::string>;
+
     /// \brief Get the object info related to a given path inside a Git tree.
     /// Unlike GetSubtreeFromTree, we here ignore errors and only return a value
     /// when all is successful.