option in packrat::init not to search all directories

Hi,

packrat::init currently searches all subdirectories of the project directory for code and tries to install things. Sometimes this causes errors (example, I have a "lib" directory in my project where I have libraries installed - from before I started using packrat). Or maybe my code has other dependencies that I currently don't want automatically installed during initialization. Therefore the following requests:

a) give an option in packrat::init not to search code for which packages are used
b) instead of an option, could also allow to set a directory that is being searched for code (part a is included in this when setting the directory to NULL)
c) make the function that searches the code for dependencies an exported function. Could be a useful tool also for other packages.

Thanks!

Start at packrat::init and trace the code-search step that discovers package dependencies. Determine how initialization should support skipping the search or limiting it to a selected directory, and whether that search function can be exposed for reuse; done means the requested behavior is covered and existing initialization behavior remains intact.