cabal install problems

[Jürgen Nicklisch-Franken]

I recently had some (well actually a lot of) troubles with cabal install
which are not over. I installed ghc-6.10 on Windows with Cygwin and the
fetched cabal-install 0.6.0. 

When I then tried to install a package it had regex-posix as dependency
it fails to install the newest version package. This was because it
doesn't find the c header files. So I tried to use the
 --extra-include-dirs=PATH flag, but this didn't help, and I guess it
was because it was the c2hs preprocessor which didn't get it. 

So I did a manual install of the package and somehow did it. But
although ghc-pkg listed the package, when I next time called cabal
install it started with installing the package that was already
installed. 
When called with a verbose flag I saw that cabal-install detected that
the package was not installed by cabal install. However why does it try
to reinstall an already installed package? How does it know, which
packages are installed with cabal install?

I then changed the version of the required regex-posix package to the
exact version of the lib pre-installed with ghc on Windows. Yet I can
never use cabal upgrade again, because it will always fail.

Is their any way to exclude a package from the cabal install process?

I realised as well that there is no way to ever un-install a package
installed with cabal-install, as far as I see. This is not satisfactory,
right?

I regret as well that no option exist to have the source code expanded
(I mean from tar.gz), which can be useful if you want to look up some
library code later, which I happen to do frequently.

I regret as well that there is no way to adopt a cabal file to my needs
when using cabal install, which I find sometimes necessary. 

As cabal install is supposed to become a standard way of installing
Haskell packages, at least for developers, it would be necessary to have
some documentation on it, other then just explaining command line
parameters.

E.g. if you install some packages as user, which it does by default, it
will later not be possible to install other packages global, which
anyone using cabal install should know. (Or am I wrong)

So please help us from spending our time with stupid install problems,
and make the road for new Haskell users as smooth as possible, and
installation is a big issue for them.

Jürgen