A new launcher came out for Minecraft on April 18, 2013. With the new launcher, the "force update" button was removed, which wasn't a problem because I haven't needed to force update the game since then. Now I do need to force update, but I don't see how I can do that. Does anybody know how I can force the game to re-download all its automatically downloaded files?
You can simply go to the Minecraft website and download the new version. If you have already logged in go to "Download Game" and select the newest version based on your computer type (ie. Mac Pc).
If you are having an issue with texture packs there is a category in options where you can add mods and remove them. Removing all the mods other than classic will return you to the original game format
If you need help deleting mods like Feed the Beast I found this short but somewhat helpful info.
If you want to uninstall FTB, depending on what computer it is, on a PC the "Modpack" file should be on the desktop but on Mac I have no idea. If you are deleting one specific modpack, look for that modpack's name and delete it, but I will say that I will not take any responsibility for your loss of saves.
If there is a specific mod to any item in the game (ie Humans) you need to go to your files and find the .zip file that holds the information. Then delete it.
as long as you haven't messed around with your Minecraft account in the new launcher it will update automatically, if you have messed with it, then you need to click the options button next to your Minecraft account and it will open a screen up, click the bar next to "use version" and select "use latest version" that should force Minecraft to automatically update. I hope this helped :)