Added annex-cost-command configuration, which can be used to vary the cost of a remote based on the output of a shell command.

Also avoided crashing if the user specified cost value cannot be parsed.

Config.hs

@@ -9,6 +9,8 @@ module Config where
 
 import Data.Maybe
 import Control.Monad.State (liftIO)
+import Control.Monad (liftM)
+import System.Cmd.Utils
 
 import qualified Git
 import qualified Annex
@@ -40,14 +42,23 @@ remoteConfig r key = "remote." ++ fromMaybe "" (Git.repoRemoteName r) ++ ".annex
 {- Calculates cost for a remote.
  -
  - The default cost is 100 for local repositories, and 200 for remote
- - repositories; it can also be configured by remote.<name>.annex-cost
+ - repositories; it can also be configured by remote.<name>.annex-cost,
+ - or if remote.<name>.annex-cost-command is set and prints a number, that
+ - is used.
  -}
 remoteCost :: Git.Repo -> Int -> Annex Int
 remoteCost r def = do
-	c <- getConfig r "cost" ""
-	if not $ null c
-		then return $ read c
-		else return def
+	cmd <- getConfig r "cost-command" ""
+	return . safeparse =<< if not $ null cmd
+			then liftM snd $ liftIO $ pipeFrom "sh" ["-c", cmd]
+			else getConfig r "cost" ""
+	where
+		safeparse v
+			| null ws || null ps = def
+			| otherwise = (fst . head) ps
+			where
+				ws = words v
+				ps = reads $ head ws
 
 cheapRemoteCost :: Int
 cheapRemoteCost = 100

debian/changelog

@@ -4,6 +4,8 @@ git-annex (3.20110818) UNRELEASED; urgency=low
     is first being created. Clones will automatically notice that git-annex
     is in use and automatically perform a basic initalization. It's
     still recommended to run "git annex init" in any clones, to describe them.
+  * Added annex-cost-command configuration, which can be used to vary the
+    cost of a remote based on the output of a shell command.
 
  -- Joey Hess <joeyh@debian.org>  Wed, 17 Aug 2011 13:44:44 -0400
 

doc/git-annex.mdwn

@@ -424,6 +424,12 @@ Here are all the supported configuration settings.
   The default cost is 100 for local repositories, and 200 for remote
   repositories.
 
+* `remote.<name>.annex-cost-command`
+
+  If set, the command is run, and the number it outputs is used as the cost.
+  This allows varying the cost based on eg, the current network. The
+  cost-command can be any shell command line.
+
 * `remote.<name>.annex-ignore`
 
   If set to `true`, prevents git-annex