This isn't cabal's fault. (Though the error message could certainly be clearer.) That message essentially means that your GHC is too old to build gitit, since the base package version is tied directly to the version of GHC.
I'm not saying this is a software bug, I'm saying it's a broken platform.
The package tells me it's version 7.0.4, released 15 June 2011. It's the version currently packaged by Fedora, and it's barely a year old. Yet it's already incompatible with new software?
Exactly. The sad thing is that I tried to install it precisely because it's the sort of thing (interesting new software[1] I want to try!) that I almost never see from the Haskell community. Yet I can't (well, won't), because the only way to use it is to build and install the bleeding edge version of the whole stinking platform from source. Yuck.
[1] Software that integrates well with the existing OS environment, to boot (again, something often sorely lacking inside the Haskell gardens). I mean, it uses git and runs as a self-contained web service. It looks nifty.
