Add example that tries to trip someone who reads something from the index

This doesn't happen here though, so nothing special we could trigger.

Author: Byron

gix-submodule/tests/file/baseline.rs

@@ -14,11 +14,12 @@ fn common_values_and_names_by_path() -> crate::Result {
     assert_eq!(
         modules
             .iter()
-            .map(|m| m.config_path().expect("present").to_owned())
+            .map(|m| { m.config_path().expect("present").to_owned() })
             .collect::<Vec<_>>(),
         [
             "empty-clone/.gitmodules",
             "multiple/.gitmodules",
+            "not-a-submodule/.gitmodules",
             "recursive-clone/.gitmodules",
             "recursive-clone/submodule/.gitmodules",
             "relative-clone/.gitmodules",

gix-submodule/tests/file/mod.rs

@@ -5,11 +5,9 @@ fn submodule(bytes: &str) -> gix_submodule::File {
 mod is_active_platform {
     use std::str::FromStr;
 
-    use bstr::{BStr, ByteSlice};
-
-    fn multi_modules() -> crate::Result<gix_submodule::File> {
+    fn module_file(name: &str) -> crate::Result<gix_submodule::File> {
         let modules = gix_testtools::scripted_fixture_read_only("basic.sh")?
-            .join("multiple")
+            .join(name)
             .join(".gitmodules");
         Ok(gix_submodule::File::from_bytes(
             std::fs::read(&modules)?.as_slice(),
@@ -18,6 +16,12 @@ mod is_active_platform {
         )?)
     }
 
+    use bstr::{BStr, ByteSlice};
+
+    fn multi_modules() -> crate::Result<gix_submodule::File> {
+        module_file("multiple")
+    }
+
     fn assume_valid_active_state<'a>(
         module: &'a gix_submodule::File,
         config: &'a gix_config::File<'static>,
@@ -52,6 +56,17 @@ mod is_active_platform {
             .collect())
     }
 
+    #[test]
+    fn without_submodule_in_index() -> crate::Result {
+        let module = module_file("not-a-submodule")?;
+        assert_eq!(
+            module.names().map(ToOwned::to_owned).collect::<Vec<_>>(),
+            ["submodule"],
+            "entries can be read"
+        );
+        Ok(())
+    }
+
     #[test]
     fn without_any_additional_settings_all_are_inactive_if_they_have_a_url() -> crate::Result {
         let module = multi_modules()?;

gix-submodule/tests/fixtures/basic.sh

@@ -37,3 +37,12 @@ git clone super recursive-clone
 (cd recursive-clone
   git submodule update --init --recursive
 )
+
+git clone super not-a-submodule
+(cd not-a-submodule
+  cp .gitmodules modules.bak
+  git rm submodule
+  echo fake > submodule
+  mv modules.bak .gitmodules
+  git add submodule && git commit -m "no submodule in index and commit, but in configuration"
+)

gix-submodule/tests/fixtures/generated-archives/basic.tar.xz

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:c961fe67eb7af352064aeae412cabf8b8260782db003ddea7ca251c491c4963e
-size 31404
+oid sha256:f1213af1023577c8c59e1a065530785e28ee10e4e04f731597aebc6a63e3dc86
+size 32472