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, 3 deletions

diff --git a/src/Propellor/Spin.hs b/src/Propellor/Spin.hs
index ecefbf6e..401c9375 100644
--- a/src/Propellor/Spin.hs
+++ b/src/Propellor/Spin.hs
@@ -40,8 +40,8 @@ commitSpin = do
 		void $ actionMessage "Push to central git repository" $
 			boolSystem "git" [Param "push"]
 
-spin :: HostName -> Maybe HostName -> Host -> IO ()
-spin target relay hst = do
+spin :: HostName -> Maybe HostName -> ControllerChain -> Host -> IO ()
+spin target relay cc hst = do
 	cacheparams <- if viarelay
 		then pure ["-A"]
 		else toCommand <$> sshCachingParams hn
@@ -89,7 +89,9 @@ spin target relay hst = do
 	runcmd = "cd " ++ localdir ++ " && ./propellor " ++ cmd
 	cmd = if viarelay
 		then "--serialized " ++ shellEscape (show (Spin [target] (Just target)))
-		else "--continue " ++ shellEscape (show (SimpleRun target))
+		else if cc == mempty
+			then "--continue " ++ shellEscape (show (SimpleRun target))
+			else "--continue " ++ shellEscape (show (ControlledRun target cc))
 
 -- Check if the Host contains an IP address that matches one of the IPs
 -- in the DNS for the HostName. If so, the HostName is used as-is,