fix: ensure vendored grammar is in a clean state

Author: RoloEdits

helix-loader/src/grammar.rs

@@ -300,6 +300,8 @@ fn fetch_grammar(grammar: GrammarConfiguration) -> Result<FetchStatus> {
                 &grammar_dir,
                 ["fetch", "--depth", "1", REMOTE_NAME, &revision],
             )?;
+            git(&grammar_dir, ["reset", "--hard"])?;
+            git(&grammar_dir, ["clean", "-fdx"])?;
             git(&grammar_dir, ["checkout", &revision])?;
 
             Ok(FetchStatus::GitUpdated { revision })