Add new redisAppendFormatedCommand with tests

Closes #202

hiredis.c

@@ -1257,6 +1257,15 @@ int __redisAppendCommand(redisContext *c, char *cmd, size_t len) {
     return REDIS_OK;
 }
 
+int redisAppendFormattedCommand(redisContext *c, char *format, size_t len) {
+
+    if (__redisAppendCommand(c, format, len) != REDIS_OK) {
+        return REDIS_ERR;
+    }
+
+    return REDIS_OK;
+}
+
 int redisvAppendCommand(redisContext *c, const char *format, va_list ap) {
     char *cmd;
     int len;

hiredis.h

@@ -194,6 +194,10 @@ int redisBufferWrite(redisContext *c, int *done);
 int redisGetReply(redisContext *c, void **reply);
 int redisGetReplyFromReader(redisContext *c, void **reply);
 
+/* Write a formatted command to the output buffer. Use these functions in blocking mode
+ * to get a pipeline of commands. */
+int redisAppendFormattedCommand(redisContext *c, char *format, size_t len);
+
 /* Write a command to the output buffer. Use these functions in blocking mode
  * to get a pipeline of commands. */
 int redisvAppendCommand(redisContext *c, const char *format, va_list ap);

test.c

@@ -217,6 +217,28 @@ static void test_format_commands(void) {
     free(cmd);
 }
 
+static void test_append_formatted_commands(struct config config) {
+    redisContext *c;
+    redisReply *reply;
+    char *cmd;
+    int len;
+
+    c = connect(config);
+
+    test("Append format command: ");
+
+    len = redisFormatCommand(&cmd, "SET foo bar");
+
+    test_cond(redisAppendFormattedCommand(c, cmd, len) == REDIS_OK);
+
+    assert(redisGetReply(c, (void*)&reply) == REDIS_OK);
+
+    free(cmd);
+    freeReplyObject(reply);
+
+    disconnect(c, 0);
+}
+
 static void test_reply_reader(void) {
     redisReader *reader;
     void *reply;
@@ -686,6 +708,7 @@ int main(int argc, char **argv) {
     test_blocking_connection(cfg);
     test_blocking_io_errors(cfg);
     test_invalid_timeout_errors(cfg);
+    test_append_formatted_commands(cfg);
     if (throughput) test_throughput(cfg);
 
     printf("\nTesting against Unix socket connection (%s):\n", cfg.unix.path);