That can be done in hackage when people try to upload. Fixes bug #127.

It generates the actual file to be passed to the compiler's package program.
This is obviously compiler-specific.

eg so we don't call cpp with ././src/blah -o ./dist/blah
since those ././ can end up in error messages.

so we don't have to individually track all the files we create
we still have to delete a few files outside of the build dir sadly
the configuration is still preserved if you specify --save-configure

There's slightly more code overally but it's no longer incomprehensible
because it's not all mixed together for all the different compilers.

Of type PackageIdentifier rather than Version.

We do this during the configure step and then later we don't have to run
haddock & hscolour again to find out their version numbers.
This also eliminates some annoying module interdependencies.
Eventually the Program abstraction ought to include the ability for programs
to discover their own version numbers so it can be done more modularly.

findProgram and findProgramAndVersion construct Program values
The latter makes it easier to parse output of --version calls.
The idea is that we should carry the version number along with the program
if we know it, so we can later decide version-dependent args without having
to do more IO to find the program version, eg see use_optP_P & haddockVersion.

So out with compilerPath :: FilePath, in with compilerProg :: Program
Similarly for compilerPkgTool.
Lots of knock-on changes due to this, including converting many more uses of
rawSystemExit to rawSystemProgram.

At the moment it's a partial function, but we should change that by having
a distinction between an abstract program and a configured program.

Now better separated and uses Program better.
Also no longer needs internal lookupProgram' utils function.

Only include ": " in the title if it has a synopsis to use as subtitle
Use the description as the prolog, or if that's empty we use the synopsis.
Do the same for executables, fixing bug #142.

It says:
> No documentation was generated as this package does not contain a library.
> Perhaps you want to use the haddock command with the --executables flag.

And make the similar message for sdist respect the verbosity

helpful.

You can now use expressions like impl( ghc >= 6.6.1 ) in conditionals
in .cabal files.

It's really a wrapper around the simple build system.