Don't quote struct field names in diff (#2177)

cmd/noms/diff/diff.go

@@ -146,10 +146,10 @@ func diffStructs(w io.Writer, p types.Path, v1, v2 types.Struct) {
 		switch change.ChangeType {
 		case types.DiffChangeAdded:
 			wroteHeader = writeHeader(w, wroteHeader, p)
-			line(w, ADD, change.V, v2.Get(fn))
+			field(w, ADD, change.V, v2.Get(fn))
 		case types.DiffChangeRemoved:
 			wroteHeader = writeHeader(w, wroteHeader, p)
-			line(w, DEL, change.V, v1.Get(fn))
+			field(w, DEL, change.V, v1.Get(fn))
 		case types.DiffChangeModified:
 			f1 := v1.Get(fn)
 			f2 := v2.Get(fn)
@@ -157,8 +157,8 @@ func diffStructs(w io.Writer, p types.Path, v1, v2 types.Struct) {
 				diff(w, p.AddField(fn), types.String(fn), f1, f2)
 			} else {
 				wroteHeader = writeHeader(w, wroteHeader, p)
-				line(w, DEL, change.V, f1)
-				line(w, ADD, change.V, f2)
+				field(w, DEL, change.V, f1)
+				field(w, ADD, change.V, f2)
 			}
 		}
 	}
@@ -203,6 +203,14 @@ func line(w io.Writer, op int, key, val types.Value) {
 	write(w, []byte("\n"))
 }
 
+func field(w io.Writer, op int, name, val types.Value) {
+	pw := newPrefixWriter(w, op)
+	write(pw, []byte(name.(types.String)))
+	write(w, []byte(": "))
+	writeEncodedValue(pw, val)
+	write(w, []byte("\n"))
+}
+
 func writeHeader(w io.Writer, wroteHeader bool, p types.Path) bool {
 	if !wroteHeader {
 		if len(p) == 0 {

cmd/noms/diff/diff_test.go

@@ -141,8 +141,8 @@ func TestNomsStructDiff(t *testing.T) {
 +   "four": "four-diff"
   }
 ["three"] {
--   "field3": "field3-data"
-+   "field3": "field3-data-diff"
+-   field3: "field3-data"
++   field3: "field3-data-diff"
 `
 
 	fieldData := []interface{}{