Allow Shopify-marked Git repositories

src/libfetchers-tests/git-utils.cc

@@ -1,5 +1,6 @@
 #include "nix/fetchers/git-utils.hh"
 #include "nix/util/file-system.hh"
+#include <git2/config.h>
 #include <gmock/gmock.h>
 #include <git2/global.h>
 #include <git2/repository.h>
@@ -66,6 +67,21 @@ void writeString(CreateRegularFileSink & fileSink, std::string contents, bool ex
     fileSink(contents);
 }
 
+TEST_F(GitUtilsTest, opens_shopify_patched_git_repository)
+{
+    git_repository * rawRepo = nullptr;
+    ASSERT_EQ(git_repository_open(&rawRepo, tmpDir.string().c_str()), 0);
+
+    git_config * config = nullptr;
+    ASSERT_EQ(git_repository_config(&config, rawRepo), 0);
+    ASSERT_EQ(git_config_set_int32(config, "core.repositoryformatversion", 1), 0);
+    ASSERT_EQ(git_config_set_bool(config, "extensions.shopifyPatchedGit", true), 0);
+    git_config_free(config);
+    git_repository_free(rawRepo);
+
+    ASSERT_NO_THROW(openRepo());
+}
+
 TEST_F(GitUtilsTest, sink_basic)
 {
     auto repo = openRepo();

src/libfetchers/git-utils.cc

@@ -137,9 +137,9 @@ static void initLibGit2()
         // Register support for additional git extensions.
         // This allows opening repos with extensions that libgit2 doesn't natively support,
         // as long as we don't actually need the extension's functionality.
-        // "refstorage" is used by reftables - we can ignore it since we only access objects by SHA.
-        const char * extensions[] = {"refstorage"};
-        git_libgit2_opts(GIT_OPT_SET_EXTENSIONS, extensions, 1);
+        // "refstorage" is used by reftables; both extensions are safe to ignore when accessing objects by SHA.
+        const char * extensions[] = {"refstorage", "shopifypatchedgit"};
+        git_libgit2_opts(GIT_OPT_SET_EXTENSIONS, extensions, 2);
     });
 }