started converting to use optparse-applicative

This is a work in progress. It compiles and is able to do basic command
dispatch, including git autocorrection, while using optparse-applicative
for the core commandline parsing.

* Many commands are temporarily disabled before conversion.
* Options are not wired in yet.
* cmdnorepo actions don't work yet.

Also, removed the [Command] list, which was only used in one place.

Command/Assistant.hs

@@ -19,10 +19,10 @@ import Assistant.Install
 
 import System.Environment
 
-cmd :: [Command]
-cmd = [noRepo checkNoRepoOpts $ dontCheck repoExists $ withOptions options $
+cmd :: Command
+cmd = noRepo checkNoRepoOpts $ dontCheck repoExists $ withOptions options $
 	notBareRepo $ command "assistant" paramNothing seek SectionCommon
-		"automatically sync changes"]
+		"automatically sync changes"
 
 options :: [Option]
 options =