check lsof at runtime

Assistant.hs

@@ -52,7 +52,6 @@ import Assistant.SanityChecker
 import qualified Annex
 import qualified Utility.Daemon
 import Utility.LogFile
-import qualified Build.SysConfig as SysConfig
 
 import Control.Concurrent
 
@@ -66,11 +65,11 @@ startDaemon foreground
 		pidfile <- fromRepo gitAnnexPidFile
 		go $ Utility.Daemon.daemonize logfd (Just pidfile) False
 	where
-		go a
-			| SysConfig.lsof = start a
-			| otherwise =
-				ifM (Annex.getState Annex.force)
+		go a = ifM (liftIO $ inPath "lsof")
+			( go a
+			, ifM (Annex.getState Annex.force)
 				(start a, needlsof)	
+			)
 		start a = withThreadState $ \st -> do
 			dstatus <- startDaemonStatus
 			liftIO $ a $ do
@@ -85,16 +84,11 @@ startDaemon foreground
 				_ <- forkIO $ sanityCheckerThread st dstatus changechan
 				watchThread st dstatus changechan
 
-		-- this message is optimised away when lsof is available
 		needlsof = error $ unlines
-			[ "The lsof command is needed for watch mode to be safe."
-			, "But this build of git-annex was made without lsof available. Giving up..."
-			, ""
-			, "You can use --force if lsof is available now. Please make very sure it is."
-			, "If run with --force and without lsof available, files can be added to the"
-			, "annex while a process still has them opened for writing. This can"
-			, "corrupt data in the annex, and make fsck complain."
-			, "Use the --force with caution, Luke!"
+			[ "The lsof command is needed for watch mode to be safe, and is not in PATH."
+			, "To override lsof checks to ensure that files are not open for writing"
+			, "when added to the annex, you can use --force"
+			, "Be warned: This can corrupt data in the annex, and make fsck complain."
 			]
 
 stopDaemon :: Annex ()

debian/control

@@ -28,7 +28,6 @@ Build-Depends:
 	uuid,
 	rsync,
 	openssh-client,
-	lsof,
 Maintainer: Joey Hess <joeyh@debian.org>
 Standards-Version: 3.9.3
 Vcs-Git: git://git.kitenet.net/git-annex

doc/install.mdwn

@@ -55,7 +55,7 @@ To build and use git-annex, you will need:
     a sha1 command will also do)
   * [gpg](http://gnupg.org/) (optional; needed for encryption)
   * [lsof](ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/)
-    (needed for watch mode)
+    (optional; recommended for watch mode)
   * [ikiwiki](http://ikiwiki.info) (optional; used to build the docs)
 
 Then just [[download]] git-annex and run: `make; make install`