[core] replace folding whitespace with a single space

- previously the leading whitespace from folded lines was kept
- also ignore lines without any data

src/request.c

@@ -1067,7 +1067,18 @@ int http_request_parse(server *srv, connection *con) {
 							goto failure;
 						}
 
-						buffer_append_string_len(current_header->value, value, value_len);
+						if (value_len > 0) {
+							/* strip leading whitespace; trailing was already removed, so can't be empty */
+							while (value_len > 0 && (value[0] == ' ' || value[0] == '\t')) {
+								value++;
+								--value_len;
+							}
+
+							if (buffer_string_length(current_header->value) > 0) {
+								buffer_append_string_len(current_header->value, CONST_STR_LEN(" "));
+							}
+							buffer_append_string_len(current_header->value, value, value_len);
+						}
 					} else {
 						/* process previous header */
 						if (current_header) {

src/t/test_request.c

@@ -229,7 +229,7 @@ static void test_request_http_request_parse(server *srv, connection *con)
       array_get_element_klen(con->request.headers, CONST_STR_LEN("Location"));
     assert(ds
            && buffer_is_equal_string(ds->value,
-                                     CONST_STR_LEN("foo, foobar  baz")));
+                                     CONST_STR_LEN("foo, foobar baz")));
 
     run_http_request_parse(srv, con, __LINE__, 0,
       "#1232 - duplicate headers with line-wrapping - test 2",
@@ -241,7 +241,7 @@ static void test_request_http_request_parse(server *srv, connection *con)
     ds = (data_string *)
       array_get_element_klen(con->request.headers, CONST_STR_LEN("Location"));
     assert(ds
-           && buffer_is_equal_string(ds->value, CONST_STR_LEN("foobar  baz")));
+           && buffer_is_equal_string(ds->value, CONST_STR_LEN("foobar baz")));
 
     run_http_request_parse(srv, con, __LINE__, 0,
       "#1232 - duplicate headers with line-wrapping - test 3",
@@ -253,7 +253,7 @@ static void test_request_http_request_parse(server *srv, connection *con)
     ds = (data_string *)
       array_get_element_klen(con->request.headers, CONST_STR_LEN("Location"));
     assert(ds
-           && buffer_is_equal_string(ds->value, CONST_STR_LEN("foobar  baz")));
+           && buffer_is_equal_string(ds->value, CONST_STR_LEN("foobar baz")));
 
     run_http_request_parse(srv, con, __LINE__, 400,
       "missing protocol",
@@ -343,7 +343,7 @@ static void test_request_http_request_parse(server *srv, connection *con)
                     "\r\n"));
     ds = (data_string *)
       array_get_element_klen(con->request.headers, CONST_STR_LEN("ABC"));
-    assert(ds && buffer_is_equal_string(ds->value, CONST_STR_LEN("foo  bc")));
+    assert(ds && buffer_is_equal_string(ds->value, CONST_STR_LEN("foo bc")));
 
     run_http_request_parse(srv, con, __LINE__, 411,
       "POST request, no Content-Length",