FileRoot: Fix parsing of ignore-special Git tree roots

When populating the GitTree instance stored in a Git tree-type
FileRoot with the ignore-special flag set, the GitTree instance
would be created with an empty raw_id_ field, signaling that some
of the entries might have been skipped and thus the root tree id
is not anymore in a one-to-one correspondence with the stored list
of entries.

This however caused FileRoot instances with missing tree id
information. This commit fixes the issue by always storing the
raw_id_ field as the root id of the Git tree, as well as clarifying
the relationship between this field and the ignore_special_ flag,
including refactoring the tree id getters.

(cherry picked from 06336198a38ffaec6c35df34580391579a7a7b22)

1 files changed, 11 insertions, 12 deletions

diff --git a/src/buildtool/file_system/file_root.hpp b/src/buildtool/file_system/file_root.hpp
index 08779e8e..eff4d450 100644
--- a/src/buildtool/file_system/file_root.hpp
+++ b/src/buildtool/file_system/file_root.hpp
@@ -225,17 +225,15 @@ class FileRoot {
             if (std::holds_alternative<tree_t>(data_)) {
                 try {
                     auto const& data = std::get<tree_t>(data_);
-                    // check if tree is ignore_special
-                    if (data->RawHash().empty()) {
-                        return std::nullopt;
-                    }
-                    auto const& id = data->Hash();
-                    auto const& size = data->Size();
-                    if (size) {
-                        return ArtifactDescription{
-                            ArtifactDigest{id, *size, /*is_tree=*/true},
-                            ObjectType::Tree,
-                            repository};
+                    // only consider tree if we have it unmodified
+                    if (auto id = data->Hash()) {
+                        auto const& size = data->Size();
+                        if (size) {
+                            return ArtifactDescription{
+                                ArtifactDigest{*id, *size, /*is_tree=*/true},
+                                ObjectType::Tree,
+                                repository};
+                        }
                     }
                 } catch (...) {
                     return std::nullopt;
@@ -351,7 +349,8 @@ class FileRoot {
                 nlohmann::json j;
                 j.push_back(ignore_special_ ? kGitTreeIgnoreSpecialMarker
                                             : kGitTreeMarker);
-                j.push_back(std::get<git_root_t>(root_).tree->Hash());
+                // we need the root tree id, irrespective of ignore_special flag
+                j.push_back(std::get<git_root_t>(root_).tree->FileRootHash());
                 return j;
             }
             if (std::holds_alternative<absent_root_t>(root_)) {