record transfer information on local git remotes

In order to record a semi-useful filename associated with the key,
this required plumbing the filename all the way through to the remotes'
storeKey and retrieveKeyFile.

Note that there is potential for deadlock here, narrowly avoided.
Suppose the repos are A and B. A sends file foo to B, and at the same
time, B gets file foo from A. So, A locks its upload transfer info file,
and then locks B's download transfer info file. At the same time,
B is taking the two locks in the opposite order. This is only not a
deadlock because the lock code does not wait, and aborts. So one of A or
B's transfers will be aborted and the other transfer will continue.
Whew!

Command/Status.hs

@@ -31,6 +31,7 @@ import Logs.Trust
 import Remote
 import Config
 import Utility.Percentage
+import Logs.Transfer
 
 -- a named computation that produces a statistic
 type Stat = StatState (Maybe (String, StatState String))
@@ -70,6 +71,7 @@ fast_stats =
 	, remote_list SemiTrusted "semitrusted"
 	, remote_list UnTrusted "untrusted"
 	, remote_list DeadTrusted "dead"
+	, transfer_list
 	, disk_size
 	]
 slow_stats :: [Stat]
@@ -170,6 +172,24 @@ bloom_info = stat "bloom filter size" $ json id $ do
 
 	return $ size ++ note
 
+transfer_list :: Stat
+transfer_list = stat "transfers in progress" $ nojson $ lift $ do
+	uuidmap <- Remote.remoteMap id
+	ts <- getTransfers
+	if null ts
+		then return "none"
+		else return $ pp uuidmap "" $ sort ts
+	where
+		pp _ c [] = c
+		pp uuidmap c ((t, i):xs) = "\n\t" ++ line uuidmap t i ++ pp uuidmap c xs
+		line uuidmap t i = unwords
+			[ show (transferDirection t) ++ "ing"
+			, fromMaybe (show $ transferKey t) (associatedFile i)
+			, if transferDirection t == Upload then "to" else "from"
+			, maybe (fromUUID $ transferRemote t) Remote.name $
+				M.lookup (transferRemote t) uuidmap
+			]
+
 disk_size :: Stat
 disk_size = stat "available local disk space" $ json id $ lift $
 	calcfree