Relax restriction on timestamp reuse in chunks, add test.

Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

pkg/chunkenc/gzip.go

@@ -82,7 +82,7 @@ func (hb *headBlock) isEmpty() bool {
 }
 
 func (hb *headBlock) append(ts int64, line string) error {
-	if !hb.isEmpty() && hb.maxt >= ts {
+	if !hb.isEmpty() && hb.maxt > ts {
 		return ErrOutOfOrder
 	}
 

pkg/chunkenc/gzip_test.go

@@ -54,6 +54,14 @@ func TestGZIPBlock(t *testing.T) {
 			ts:  8,
 			str: "hello, worl\nd8!",
 		},
+		{
+			ts:  8,
+			str: "hello, world 8, 2!",
+		},
+		{
+			ts:  8,
+			str: "hello, world 8, 3!",
+		},
 		{
 			ts:  9,
 			str: "",