If you get error 413, then the issue doesn’t lie with git but with your web server.
It’s your web server that is blocking big upload files.
Solution for nginx
Just load your nginx.conf and add client_max_body_size 50m; ( changing the value to your needs ) in the http block.
Reload nginx to accept the new config by executing sudo service nginx reload and try again to push your commit over http.
Solution for Apache
In your httpd.conf add LimitRequestBody 52428800 ( changing the value to your needs ) inside a <Directory /> block. Doing this you can limit the request of the whole server filesystem, just a single Virtual Host or a directory.
I hope this helps.