fix: address PR review comments for rewriteChartDependencies

- Handle non-NotExist errors from st.fs.Stat to surface permission/IO failures
- Reword function doc to clarify temp copy is conditional on rewrite being needed
- Assert rewrittenPath vs tempDir based on expectModified in test table

Signed-off-by: yxxhero <aiopsclub@163.com>

pkg/state/chart_dependencies_rewrite_test.go

@@ -209,6 +209,16 @@ extra-field: aaa
 				return
 			}
 
+			if tt.expectModified {
+				if rewrittenPath == tempDir {
+					t.Errorf("expected rewrittenPath != tempDir when modifications are needed, got same path")
+				}
+			} else {
+				if rewrittenPath != tempDir {
+					t.Errorf("expected rewrittenPath == tempDir when no modifications are needed, got %q", rewrittenPath)
+				}
+			}
+
 			if err != nil {
 				t.Fatalf("unexpected error: %v", err)
 			}

pkg/state/state.go

@@ -1410,15 +1410,18 @@ type PrepareChartKey struct {
 // rewriteChartDependencies rewrites relative file:// dependencies in Chart.yaml to absolute paths
 // to ensure they can be resolved from chartify's temporary directory.
 // Instead of modifying the original chart in-place (which causes race conditions when multiple
-// releases reference the same local chart), it copies the chart to a temporary directory and
-// rewrites the copy. Each call creates a fresh temp copy reflecting the current chart contents,
-// so prepare hooks or other steps that mutate the local chart directory are always honored.
-// The returned cleanup function removes the temporary directory when called.
+// releases reference the same local chart), it creates a temporary copy only when a rewrite is
+// needed and rewrites that copy. When a temp copy is created, it reflects the current chart
+// contents so prepare hooks or other steps that mutate the local chart directory are honored.
+// The returned cleanup function removes the temporary directory when one was created and is
+// otherwise a no-op.
 func (st *HelmState) rewriteChartDependencies(chartPath string) (string, func(), error) {
 	chartYamlPath := filepath.Join(chartPath, "Chart.yaml")
 
 	if _, err := st.fs.Stat(chartYamlPath); os.IsNotExist(err) {
 		return chartPath, func() {}, nil
+	} else if err != nil {
+		return chartPath, func() {}, err
 	}
 
 	data, err := st.fs.ReadFile(chartYamlPath)