Fairly often I encounter some problems in my project that makes me want to undo the last changes to it. But the “undo”-option under the “edit”-menu is not quite as good as expected. And anyway I would like to make at least daily backups of the project. But how do I do that? How do I make a copy or backup of the project somewhere on my harddrive?
I just zip the whole project folder periodically. It’s probably best to make sure it isn’t open in Unity before you do that, though.
You could also use Leopard’s Time Machine feature, although I’d suggest that you only use it to restore the whole project in one go, or to manually pull a complete previous version out of its backup folders. Trying to restore just part of a project might damage it.
So the best way is to make a hardcopy of the entire project and save it somewhere?
And then if I have to reopen it again then just overwrite the last files with the hardcopied version?
The simplest way is to copy/zip the whole project folder. The best way would presumably be to get a license for the Asset Server, although that costs an additional $500.
If you just copy the project folder, you can either overwrite the original version with it (again, while it isn’t open in Unity) or you can just open the copy from wherever it happens to be (by double clicking one of its scene files, for example).
EDIT: I should probably mention that it’s a bad idea to pull random files out of a Unity project. You can pull out isolated asset and script files, but you shouldn’t drag Unity-specific files, such as prefabs or scenes, into other projects. If you do, links will be broken and you won’t be able to use those objects properly. Instead, if you need to get some complicated assembly out of an old version of a project and into the latest version, you should export a package from the old one and import it into the new, just as you would between unrelated projects.
I don’t think you wanna make a hardcopy of any Unity project. Hardcopy = paper printout. 
Anyway, I do the simple thing and just copy the project folder. Any in-progress projects usually end up with multiple copies, just in case. (Which I’ve never needed, but the one time I don’t do that, you know what’s going to happen…)
–Eric
I simply (almost daily) just back the whole project folder to an external drive into a dated and numbered folder in the case of Widget United. I’ve once or twice had to do a restore like this after my attempts at fixing some code have resulted in spectacular, uh, problems.
Okay…cool. Then this must be the way to do it.
Just chiming in. I use Time Machine for backup with an external drive. I’ve also made dated unity packages from my project, but I don’t do that on a regular basis.
I have managed to successfully roll back individual assets such as a prefab using Time Machine, but it was not a deep change (meaning that there were not a bunch of other items related to it).
So it can be done, but as others have said, Your Milage May Vary.
If you can afford it, buying the Asset Server seat and setting it up on your local machine (same one as you develop on) will provide you with a full-fledged backup and ability to roll back and recover deleted assets.
I also zip my project at critical times. One thing to keep in mind is that if you unzip it and name the folder anything else besides the original name, Unity will go about reimporting everything when you open the project. If it’s a big project with a lot of models, animations, and textures, this can take a long time. So be prepared.