Optimize zlib reader and consolidate sync.pools

Expands on the optimisations from https://github.com/fluxcd/go-git/pull/5
and ensures that zlib reader does not need to recreate a deflate
dictionary at every use.

The use of sync pools was consolidated into a new sync utils package.

name       old time/op    new time/op    delta
Parser-16    7.51ms ± 3%    7.71ms ± 6%     ~     (p=0.222 n=5+5)

name       old alloc/op   new alloc/op   delta
Parser-16    4.65MB ± 3%    1.90MB ± 3%  -59.06%  (p=0.008 n=5+5)

name       old allocs/op  new allocs/op  delta
Parser-16     3.48k ± 0%     3.32k ± 0%   -4.57%  (p=0.016 n=5+4)

Signed-off-by: Paulo Gomes <pjbgf@linux.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/utils/sync/bufio_test.go b/utils/sync/bufio_test.go
new file mode 100644
index 0000000..e70f3d8
--- /dev/null
+++ b/utils/sync/bufio_test.go
@@ -0,0 +1,26 @@
+package sync
+
+import (
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestGetAndPutBufioReader(t *testing.T) {
+	wanted := "someinput"
+	r := GetBufioReader(strings.NewReader(wanted))
+	if r == nil {
+		t.Error("nil was not expected")
+	}
+
+	got, err := r.ReadString(0)
+	if err != nil && err != io.EOF {
+		t.Errorf("unexpected error reading string: %v", err)
+	}
+
+	if wanted != got {
+		t.Errorf("wanted %q got %q", wanted, got)
+	}
+
+	PutBufioReader(r)
+}