dashboard/app: email regressions in files only

The lines about folders don't look actionable.

Author: tarasmadan

dashboard/app/reporting_email.go

@@ -208,8 +208,10 @@ func coverageTable(ctx context.Context, ns string, fromTo []coveragedb.TimePerio
 		FilterMinCoveredLinesDrop: minDrop,
 	})
 	res := "Blocks diff,\tPath\n"
-	templData.Root.Visit(func(path string, summary int64) {
-		res += fmt.Sprintf("% 11d\t%s\n", summary, path)
+	templData.Root.Visit(func(path string, summary int64, isDir bool) {
+		if !isDir {
+			res += fmt.Sprintf("% 11d\t%s\n", summary, path)
+		}
 	})
 	return res, nil
 }

dashboard/app/reporting_test.go

@@ -1413,7 +1413,6 @@ func TestCoverageRegression(t *testing.T) {
 Web version: `+wantLink+`
 
 Blocks diff,	Path
-       -100	
        -100	/file_name.c
 
 `, msg.Body)

pkg/cover/heatmap.go

@@ -145,9 +145,9 @@ func (thm *templateHeatmapRow) prepareDataFor(pageColumns []pageColumnTarget) {
 	}
 }
 
-func (thm *templateHeatmapRow) Visit(v func(string, int64), path ...string) {
+func (thm *templateHeatmapRow) Visit(v func(string, int64, bool), path ...string) {
 	curPath := append(path, thm.Name)
-	v(strings.Join(curPath, "/"), thm.Summary)
+	v(strings.Join(curPath, "/"), thm.Summary, thm.IsDir)
 	for _, item := range thm.Items {
 		item.Visit(v, curPath...)
 	}