fs: Add IsRegularFile()

internal/fs/helpers.go

@@ -0,0 +1,13 @@
+package fs
+
+import "os"
+
+// IsRegularFile returns true if fi belongs to a normal file. If fi is nil,
+// false is returned.
+func IsRegularFile(fi os.FileInfo) bool {
+	if fi == nil {
+		return false
+	}
+
+	return fi.Mode()&(os.ModeType|os.ModeCharDevice) == 0
+}