Enforce path conversion on windows gnu, it doesn't seem to like slash…

…es (#298)

git-ref/src/store/file/find.rs

@@ -124,11 +124,18 @@ impl file::Store {
         };
         let relative_path = base.join(inbetween).join(relative_path);
 
+        let path_to_open = git_features::path::from_byte_slice_or_panic_on_windows(
+            git_features::path::convert::to_native_separators(git_features::path::into_bytes_or_panic_on_windows(
+                &relative_path,
+            ))
+            .as_ref(),
+        )
+        .to_owned();
         let contents = match self
-            .ref_contents(&relative_path)
+            .ref_contents(&path_to_open)
             .map_err(|err| Error::ReadFileContents {
                 err,
-                path: relative_path.to_owned(),
+                path: path_to_open.to_owned(),
             })? {
             None => {
                 if is_definitely_absolute {