Basically: In development mode, it runs a proxy (called the "harness") that watches your source for changes and recompiles/restarts your server on the next request, if necessary, using the "go build" tool. The go build process is incremental, so in theory should only recompile packages that have changed (and those that depend on them)
Here is a description of how it works: http://robfig.github.com/revel/manual/howrevelworks.html
Basically: In development mode, it runs a proxy (called the "harness") that watches your source for changes and recompiles/restarts your server on the next request, if necessary, using the "go build" tool. The go build process is incremental, so in theory should only recompile packages that have changed (and those that depend on them)