go/doc: permit a package synopsis to end with ":\n".

R=gri, r
CC=golang-dev
https://golang.org/cl/12822043

src/pkg/go/doc/synopsis.go

@@ -10,12 +10,15 @@ import (
 )
 
 // firstSentenceLen returns the length of the first sentence in s.
-// The sentence ends after the first period followed by space and
+// The sentence ends at the first colon followed by a newline,
-// not preceded by exactly one uppercase letter.
+// or at the first period followed by space and not preceded by
-//
+// exactly one uppercase letter.
 func firstSentenceLen(s string) int {
 	var ppp, pp, p rune
 	for i, q := range s {
+		if p == ':' && q == '\n' {
+			return i
+		}
 		if q == '\n' || q == '\r' || q == '\t' {
 			q = ' '
 		}

src/pkg/go/doc/synopsis_test.go

@@ -29,6 +29,7 @@ var tests = []struct {
 	{"Package Καλημέρα κόσμε.", 36, "Package Καλημέρα κόσμε."},
 	{"Package こんにちは 世界\n", 31, "Package こんにちは 世界"},
 	{"Package foo does bar.", 21, "Package foo does bar."},
+	{"Package foo does these things:\n  - a\n  - b", 30, "Package foo does these things:"},
 	{"Copyright 2012 Google, Inc. Package foo does bar.", 27, ""},
 	{"All Rights reserved. Package foo does bar.", 20, ""},
 	{"All rights reserved. Package foo does bar.", 20, ""},