Explain why `tests/pretty/` is unformatted.
diff --git a/rustfmt.toml b/rustfmt.toml
index 998bcb9..7cc029d 100644
--- a/rustfmt.toml
+++ b/rustfmt.toml
@@ -15,7 +15,7 @@
"/tests/crashes/", # Many of these tests contain syntax errors.
"/tests/debuginfo/", # These tests are somewhat sensitive to source code layout.
"/tests/incremental/", # These tests are somewhat sensitive to source code layout.
- "/tests/pretty/",
+ "/tests/pretty/", # These tests are very sensitive to source code layout.
"/tests/run-make/translation/test.rs", # This test contains syntax errors.
"/tests/run-make-fulldeps/",
"/tests/run-pass-valgrind/",
