[RFC PATCH 1/3] t0009: add tests to cover more error reporting scenarios

@@ -74,4 +74,40 @@ test_expect_success 'setup: .git as an empty directory is ignored' '
 	)
 '
 
+test_expect_success 'setup: custom git directory with missing HEAD is rejected' '
+	test_when_finished "rm -rf parent/empty-dir" &&
+	mkdir -p parent/empty-dir &&
+	(
+		test_must_fail git --git-dir parent/empty-dir rev-parse --is-bare-repository 2>stderr &&
+		test_grep "not a git repository" stderr
+	)
+'
+
+test_expect_success 'setup: custom git directory with HEAD as a symlink outside refs/ is rejected' '
+	test_when_finished "rm -rf parent/head-as-link-to-garbage" &&
+	mkdir -p parent/head-as-link-to-garbage &&
+	(
+		cd parent/head-as-link-to-garbage &&
+		git init --bare real-repo &&
+		touch garbage &&
+		rm real-repo/HEAD &&
+		ln -s ../garbage real-repo/HEAD &&
+		test_must_fail git --git-dir real-repo rev-parse --is-bare-repository 2>stderr &&
+		test_grep "not a git repository" stderr
+	)
+'
+
+test_expect_success 'setup: custom git directory with invalid GIT_OBJECT_DIRECTORY configuration is rejected' '
+	test_when_finished "rm -rf parent/invalid-git-object-directory-config" &&
+	mkdir -p parent/invalid-git-object-directory-config &&
+	(
+		cd parent/invalid-git-object-directory-config &&
+		git init --bare real-repo &&
+		test_must_fail env GIT_OBJECT_DIRECTORY="$(pwd)/does-not-exist" \
+			git --git-dir real-repo rev-parse --is-bare-repository 2>stderr &&
+		test_grep "not a git repository" stderr
+	)
+'
+
+
 test_done