Edit2: Jeesh... TurtoiseGit is once more stuck on 7%.... And that's 24.5mb... at that rate, the entire source code is 350mb, and presumably that does not include the dependencies, as I downloaded them separately... What makes it so huge? Any way to do it better?
The entire repository is around 300 MiB uncompressed, git compresses everything it sends, and from memory a git clone of the repo should be ~75 MiB.
It contains all revision history, which increases the size somewhat, but git is very efficient with that too (you can do a 'shallow' clone, ignoring all the history, in tortoise's clone dialog use the 'depth' option (set to 0)). Most of the space is taken up by the contents of the data directory though (ie, magitech), and a shallow clone is not likely to be much smaller than a regular one.
You could also download just the source, bypassing git...
current 'head' (< 1 MiB), this option requires a new download to update of course... and your own data to point the built binary at. To get the 'latest' at any time later,
go here and select the 'source' folder, then click the 'snapshot' link.
Note on dependencies: If you only want to build the game (and not the tools), you only need windeps_base.zip (5.4 MB).
Note on Code::Blocks and Windows: no one had tried this yet as I am aware... so assistance may be hard to come by, I'm planning to try Eclipse CDT on windows one day, which I now use on linux, but to be honest this is unlikely to happen any time soon, as I simply don't need it (or want it really... its nice, but doesn't come close to visual studio...)