thephpleague/flysystem — pull request #140 by Turneliusz (2014-05-08 11:40:26+00:00)
Title: Trying to guess MIME Type using file extension for "plain/text"

When putting CSS to AWS S3 "Fileinfo" returns the MIME Type "plain/text". That pull request creates a feature of guessing MIME Type using extension when that situation occurs, so S3 will have a proper MIME Type setup for object.