reproduce #5099, adding a submodule as project fails

Author: Byron

crates/gitbutler-project/tests/fixtures/various-repositories.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+git init simple
+(cd simple
+  >file && git add file && git commit -m "init"
+)
+
+git clone simple submodule
+
+git clone simple with-submodule
+(cd with-submodule
+  git submodule add ../submodule
+  git commit -m "add submodule"
+)

crates/gitbutler-project/tests/projects/main.rs

@@ -24,6 +24,18 @@ mod add {
     mod error {
         use super::*;
 
+        #[test]
+        fn submodule() {
+            let (controller, _tmp) = new();
+            let root = gitbutler_testsupport::gix_testtools::scripted_fixture_read_only(
+                "various-repositories.sh",
+            )
+            .unwrap()
+            .join("with-submodule");
+            let err = controller.add(root).unwrap_err();
+            assert_eq!(err.to_string(), "TBD");
+        }
+
         #[test]
         fn missing() {
             let (controller, _tmp) = new();

crates/gitbutler-testsupport/src/lib.rs

@@ -1,6 +1,11 @@
 #![forbid(rust_2018_idioms)]
 pub const VAR_NO_CLEANUP: &str = "GITBUTLER_TESTS_NO_CLEANUP";
 
+/// Direct access to lower-level utilities for cases where this is enough.
+///
+/// Prefer to use [`read_only`] and [`writable`] otherwise.
+pub use gix_testtools;
+
 mod test_project;
 pub use test_project::TestProject;