Added Propellor.Property.Spin, which can be used to make a host be a controller of other hosts.

The hard part of this is avoiding loops of controllers. To make that work,
a ControllerChain is passed to the host that's spun, and is added to the
Info of the host being spun, where the controller property can check it
to detect an avoid a loop.

That needed an expansion of the CmdLine data type. I made the new
ControlledRun only be used when there is a ControllerChain provided.
This avoids breaking backwards compatability with old propellor
deployments, as --spin still uses SimpleRun.

Note: Making an old propellor deployment be controlled by a controller
won't work until it's been updated to this commit, so it knows about
the ControlledRun parameter.

(Untested)

1 files changed, 5 insertions, 2 deletions

diff --git a/src/Propellor/CmdLine.hs b/src/Propellor/CmdLine.hs
index 33bb0bdc..35929ea7 100644
--- a/src/Propellor/CmdLine.hs
+++ b/src/Propellor/CmdLine.hs
@@ -115,11 +115,14 @@ defaultMain hostlist = do
 	go True cmdline = updateFirst cmdline $ go False cmdline
 	go False (Spin hs r) = do
 		commitSpin
-		forM_ hs $ \hn -> withhost hn $ spin hn r
+		forM_ hs $ \hn -> withhost hn $
+			spin hn r mempty
 	go False cmdline@(SimpleRun hn) = buildFirst cmdline $
 		go False (Run hn)
+	go False cmdline@(ControlledRun hn cc) = buildFirst cmdline $
+		onlyprocess $ withhost hn $ mainProperties cc
 	go False (Run hn) = ifM ((==) 0 <$> getRealUserID)
-		( onlyprocess $ withhost hn mainProperties
+		( onlyprocess $ withhost hn $ mainProperties mempty
 		, go True (Spin [hn] Nothing)
 		)