Make source generation part of the main build

[Geogi]

SBT has a sourceGenerators hook (task) that can be used to run the source generation before the main build.

This can be achieved by putting the code of Generate into the main Build.scala, taking a directory parameter, returning the sequence of generated files, and registering the hook in the main build.sbt. A work-around has to be made to inject SBT's classpath into Scalate's. See ab4aa9bd6a575b0ce0fed21e0dc9aa653d2467a7 for an almost working stub.

However, this won't work because of a Scala version mismatch:

• Either SBT is left on its default 2.9.2 version, compiles the plugin in 2.9.2 then tries to run it with the 2.10.1 Scala of the main project, which fails due to standard library changes,
• Or SBT is forced to 2.10.1 which immediately fails for obscure reasons (since SBT for 2.10 seems to exist).

It'd be nice to solve that because it would simplify the build process (by making SBT as simple as Maven was before we got macros and code gen, compiling with a single command), but that's not a priority.

[Geogi]

https://groups.google.com/forum/?fromgroups=#!topic/simple-build-tool/iCCuekP2ouE

This looks promising.

[Geogi]

Alternatively (and probably better): let generate be a separate project and add a custom task that monitors file changes on *.ssp, then run Generate on those files. Make that task part of source-generate, compile or whatever in the main build.