Add common interface for pquery

[hololeap]

This is being used in various places, such as revdep-scanner.

A new subproject inside the cabal-portage project is a good place for this (gentoo-utils?). It should include:

• A common interface for running commands

  • A re-worked runOpaque using the common error-handling interface

  • A re-worked runTransparent using the common error-handling interface

  • A common interface for handling errors (just an example):

    -- exits with a RunProcessException or else returns captured stdout and stderr
    tryProcess -- better name?
        :: Exception e
        -- Nothing is passed to stdin
        => Maybe (ConduitT ByteString ByteString IO ()) -- extra stuff using stdout (useful for e.g. runTransparent)
        -> Maybe (ConduitT ByteString ByteString IO ()) -- extra stuff using stderr (useful for e.g. runTransparent)
        -> Maybe (ExitCode -> Lazy.Text -> Lazy.Text -> IO (Maybe RunProcessException)) -- tweak exception throwing
        -> CreateProcess -- command to run, arguments, and extra settings
        -> IO (Either RunProcessException (Lazy.Text, Lazy.Text))
    
    data RunProcessException = RPE
        { rpeCP :: CreateProcess
        , rpeExitCode :: ExitCode
        , rpeStdout :: Lazy.Text
        , rpeStderr :: Lazy.Text
        }

  • Should handle errors by displying the command that was run, the exit code, the captured stdout, and the captured stderr, along with any other exceptions thrown.

• Convenience functions for running common commands, such as pquery, eix, and emerge

• Convenience functions for running pquery and parsing the output to e.g. HashMaps

• Orphan instances for portage-hs types (e.g. Hashable) to keep its dependency footprint low