tar: fix Go 1.10 breakage

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>

test/sharness/t0090-get.sh

@@ -125,6 +125,26 @@ test_get_cmd() {
     test_must_fail ipfs get ../.. 2>actual &&
     test_cmp expected actual
   '
+
+  test_expect_success "create small file" '
+    echo "foo" > small &&
+    ipfs add -q small > hash_small
+  '
+
+  test_expect_success "get small file" '
+    ipfs get -o out_small $(cat hash_small) &&
+    test_cmp small out_small
+  '
+
+  test_expect_success "create medium file" '
+    head -c 16000 > medium &&
+    ipfs add -q medium > hash_medium
+  '
+
+  test_expect_success "get medium file" '
+    ipfs get -o out_medium $(cat hash_medium) &&
+    test_cmp medium out_medium
+  '
 }
 
 test_get_fail() {

thirdparty/tar/extractor.go

@@ -114,18 +114,19 @@ func copyWithProgress(to io.Writer, from io.Reader, cb func(int64) int64) error
 	buf := make([]byte, 4096)
 	for {
 		n, err := from.Read(buf)
+		if n != 0 {
+			cb(int64(n))
+			_, err2 := to.Write(buf[:n])
+			if err2 != nil {
+				return err2
+			}
+		}
 		if err != nil {
 			if err == io.EOF {
 				return nil
 			}
 			return err
 		}
-
-		cb(int64(n))
-		_, err = to.Write(buf[:n])
-		if err != nil {
-			return err
-		}
 	}
 
 }