1 file changed, 17 insertions, 3 deletions

diff --git a/source/ui-diff.h b/source/ui-diff.h
index 39264a1..67d33ba 100644
--- a/source/ui-diff.h
+++ b/source/ui-diff.h
@@ -1,5 +1,19 @@
-#ifndef UI_DIFF_H
-#define UI_DIFF_H
+/*
+ * The page that shows what one revision changed against another, and the
+ * options panel that sits above it. The side by side renderer in ui-ssdiff
+ * builds a link on every line number, so the two revisions being compared and
+ * the file pair being rendered are published here for it rather than kept
+ * private to the page.
+ */
+
+#ifndef CGIT_UI_DIFF_H
+#define CGIT_UI_DIFF_H
+
+#include "cgit.h"
+
+// Widest context the options panel offers, and so the widest a request may
+// ask for, since the query string is clamped against it before the page runs.
+#define MAX_DIFF_CONTEXT_LINES 40
 
 extern void cgit_print_diff_ctrls(void);
 
@@ -12,4 +26,4 @@ extern struct diff_filespec *cgit_get_current_new_file(void);
 extern struct object_id old_rev_oid[1];
 extern struct object_id new_rev_oid[1];
 
-#endif /* UI_DIFF_H */
+#endif // CGIT_UI_DIFF_H