push: respect --no-thin

- From the beginning of push.c in 755225d, 2006-04-29, "thin" option
  was enabled by default but could be turned off with --no-thin.

- Then Shawn changed the default to 0 in favor of saving server
  resources in a4503a1, 2007-09-09. --no-thin worked great.

- One day later, in 9b28851 Daniel extracted some code from push.c to
  create transport.c. He (probably accidentally) flipped the default
  value from 0 to 1 in transport_get().

From then on --no-thin is effectively no-op because git-push still
expects the default value to be false and only calls
transport_set_option() when "thin" variable in push.c is true (which
is unnecessary). Correct the code to respect --no-thin by calling
transport_set_option() in both cases.

receive-pack learns about --reject-thin-pack-for-testing option,
which only is for testing purposes, hence no document update.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/receive-pack.c

@@ -38,6 +38,7 @@ static int quiet;
 static int prefer_ofs_delta = 1;
 static int auto_update_server_info;
 static int auto_gc = 1;
+static int fix_thin = 1;
 static const char *head_name;
 static void *head_name_to_free;
 static int sent_capabilities;
@@ -869,7 +870,8 @@ static const char *unpack(int err_fd)
 		keeper[i++] = "--stdin";
 		if (fsck_objects)
 			keeper[i++] = "--strict";
-		keeper[i++] = "--fix-thin";
+		if (fix_thin)
+			keeper[i++] = "--fix-thin";
 		keeper[i++] = hdr_arg;
 		keeper[i++] = keep_arg;
 		keeper[i++] = NULL;
@@ -975,6 +977,10 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 				stateless_rpc = 1;
 				continue;
 			}
+			if (!strcmp(arg, "--reject-thin-pack-for-testing")) {
+				fix_thin = 0;
+				continue;
+			}
 
 			usage(receive_pack_usage);
 		}