git-annex-shell: Don't let configlist auto-init repository when in readonly mode.

This was potentially a hole in the readonly mode armor even before my last
commit. If the user could push a git-annex branch to a repo, they could get
git-annex-shell to initialize the repo. After my last commit, the user
didn't even need to be allowed to push a branch to init the repo, so
this hole certianly needs to be closed now.

Command/ConfigList.hs

@@ -15,6 +15,7 @@ import qualified Annex.Branch
 import qualified Git.Config
 import Remote.GCrypt (coreGCryptId)
 import qualified CmdLine.GitAnnexShell.Fields as Fields
+import CmdLine.GitAnnexShell.Checks
 
 cmd :: Command
 cmd = noCommit $ dontCheck repoExists $
@@ -44,6 +45,7 @@ findOrGenUUID = do
 		then return u
 		else ifM (Annex.Branch.hasSibling <||> (isJust <$> Fields.getField Fields.autoInit))
 			( do
+				liftIO checkNotReadOnly
 				initialize Nothing
 				getUUID
 			, return NoUUID