lib/PublicInbox/ViewDiff.pm | 4 ++++

diff --git a/lib/PublicInbox/ViewDiff.pm b/lib/PublicInbox/ViewDiff.pm
index a773e385a33b8e9fcdc351e1a10cb460026e95de..0cce952d99011800e94904c80728f8911bc1278c 100644
--- a/lib/PublicInbox/ViewDiff.pm
+++ b/lib/PublicInbox/ViewDiff.pm
@@ -15,12 +15,16 @@ use URI::Escape qw(uri_escape_utf8);
 use PublicInbox::Hval qw(ascii_html to_attr from_attr);
 use PublicInbox::Git qw(git_unquote);
 
+# keep track of state so we can avoid redundant HTML tags for
+# identically-classed lines
 sub DSTATE_INIT () { 0 }
 sub DSTATE_STAT () { 1 }
 sub DSTATE_HEAD () { 2 } # /^diff --git /, /^index /, /^--- /, /^\+\+\+ /
 sub DSTATE_CTX () { 3 } # /^ /
 sub DSTATE_ADD () { 4 } # /^\+/
 sub DSTATE_DEL () { 5 } # /^\-/
+
+# maps the DSTATE_* to CSS class names compatible with what cgit uses:
 my @state2class = (
 	'', # init
 	'', # stat