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.

1 files changed, 4 insertions, 7 deletions

diff --git a/src/buildtool/file_system/git_tree.cpp b/src/buildtool/file_system/git_tree.cpp
index a5a3262d..e7a2f41d 100644
--- a/src/buildtool/file_system/git_tree.cpp
+++ b/src/buildtool/file_system/git_tree.cpp
@@ -88,12 +88,10 @@ auto GitTree::Read(gsl::not_null<GitCASPtr> const& cas,
                                               check_symlinks,
                                               /*is_hex_id=*/false,
                                               ignore_special)) {
-                // the raw_id value is NOT recomputed when ignore_special==true,
-                // so we set it to empty to signal that it should not be used!
-                return GitTree::FromEntries(cas,
-                                            std::move(*entries),
-                                            ignore_special ? "" : *raw_id,
-                                            ignore_special);
+                // NOTE: the raw_id value is NOT recomputed when
+                // ignore_special==true.
+                return GitTree::FromEntries(
+                    cas, std::move(*entries), *raw_id, ignore_special);
             }
         }
         else {
@@ -164,7 +162,6 @@ auto GitTreeEntry::Tree(bool ignore_special) const& noexcept
                                                   check_symlinks,
                                                   /*is_hex_id=*/false,
                                                   ignore_special)) {
-                    // the raw_id value is not used when ignore_special==true
                     return GitTree::FromEntries(
                         cas_, std::move(*entries), raw_id_, ignore_special);
                 }