git: use forward slashes in relative path to backing git repo

Closes #2403.

lib/src/git_backend.rs

@@ -138,8 +138,20 @@ impl GitBackend {
         let extra_path = store_path.join("extra");
         fs::create_dir(&extra_path).context(&extra_path)?;
         let target_path = store_path.join("git_target");
-        fs::write(&target_path, git_repo_path.to_str().unwrap().as_bytes())
-            .context(&target_path)?;
+        if cfg!(windows) && git_repo_path.is_relative() {
+            // WSL doesn't like backslashes in paths, so we manually format the path with
+            // forward slsashes (non-WSL is fine with forward slashes). If the path is
+            // absolute, there's much we can do - it simply won't work on both inside and
+            // outside WSL.
+            let git_repo_path_string = git_repo_path
+                .components()
+                .map(|component| component.as_os_str().to_str().unwrap().to_owned())
+                .join("/");
+            fs::write(&target_path, git_repo_path_string.as_bytes()).context(&target_path)?;
+        } else {
+            fs::write(&target_path, git_repo_path.to_str().unwrap().as_bytes())
+                .context(&target_path)?;
+        };
         let repo = git2::Repository::open(store_path.join(git_repo_path))
             .map_err(GitBackendInitError::OpenRepository)?;
         let extra_metadata_store = TableStore::init(extra_path, HASH_LENGTH);