cmd/doc: print BUGs after package docs

Was otherwise absent unless bound to an exported symbol,
as in the BUG with strings.Title.

Fixes #10781.

Change-Id: I1543137073a9dee9e546bc9d648ca54fc9632dde
Reviewed-on: https://go-review.googlesource.com/9899Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/doc/pkg.go

@@ -190,6 +190,7 @@ func (pkg *Package) packageDoc() {
 	pkg.valueSummary(pkg.doc.Vars)
 	pkg.funcSummary(pkg.doc.Funcs)
 	pkg.typeSummary()
+	pkg.bugs()
 }
 
 // packageClause prints the package clause.
@@ -253,6 +254,18 @@ func (pkg *Package) typeSummary() {
 	}
 }
 
+// bugs prints the BUGS information for the package.
+// TODO: Provide access to TODOs and NOTEs as well (very noisy so off by default)?
+func (pkg *Package) bugs() {
+	if pkg.doc.Notes["BUG"] == nil {
+		return
+	}
+	pkg.Printf("\n")
+	for _, note := range pkg.doc.Notes["BUG"] {
+		pkg.Printf("%s: %v\n", "BUG", note.Body)
+	}
+}
+
 // findValues finds the doc.Values that describe the symbol.
 func (pkg *Package) findValues(symbol string, docValues []*doc.Value) (values []*doc.Value) {
 	for _, value := range docValues {