tabwriter: indicate section breaks if Debug flag is set

R=rsc
CC=golang-dev
https://golang.org/cl/224057

src/pkg/tabwriter/tabwriter.go

@@ -281,6 +281,7 @@ func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int, err os.Error)
 			c := line.At(j).(cell)
 
 			if j > 0 && b.flags&Debug != 0 {
+				// indicate column break
 				if err = b.write0(vbar); err != nil {
 					return
 				}
@@ -496,6 +497,8 @@ func (b *Writer) Flush() os.Error {
 }
 
 
+var hbar = []byte{'-', '-', '-', '\n'}
+
 // Write writes buf to the writer b.
 // The only errors returned are ones encountered
 // while writing to the underlying output stream.
@@ -525,6 +528,12 @@ func (b *Writer) Write(buf []byte) (n int, err os.Error) {
 						if err = b.Flush(); err != nil {
 							return
 						}
+						if ch == '\f' && b.flags&Debug != 0 {
+							// indicate section break
+							if err = b.write0(hbar); err != nil {
+								return
+							}
+						}
 					}
 				}
 

src/pkg/tabwriter/tabwriter_test.go

@@ -318,6 +318,7 @@ var tests = []entry{
 			"11\t222\t3333\t44444\n",
 
 		"1|2|3|4\n" +
+			"---\n" +
 			"11|222|3333|44444\n",
 	},