documentation of using isErrorOnly

Author: lainio

assert/asserter.go

@@ -54,6 +54,8 @@ const officialTestOutputPrefix = "    "
 // Note. We use the pattern where we build defaultMsg argument reaady in cases
 // like 'got: X, want: Y'. This hits two birds with one stone: we have automatic
 // and correct assert messages, and we can add information to it if we want to.
+// If asserter is Plain (isErrorOnly()) user wants to override automatic assert
+// messgages with our given, usually simple message.
 func (asserter Asserter) reportAssertionFault(defaultMsg string, a []any) {
 	if asserter.hasStackTrace() {
 		if asserter.isUnitTesting() {