sync: Don't fail if the directory it is run in gets removed by the sync.

Command/Merge.hs

@@ -11,7 +11,7 @@ import Common.Annex
 import Command
 import qualified Annex.Branch
 import qualified Git.Branch
-import Command.Sync (mergeLocal)
+import Command.Sync (prepMerge, mergeLocal)
 
 def :: [Command]
 def = [command "merge" paramNothing seek SectionMaintenance
@@ -35,4 +35,5 @@ mergeBranch = do
 mergeSynced :: CommandStart
 mergeSynced = do
 	branch <- inRepo Git.Branch.current
+	prepMerge
 	maybe stop mergeLocal branch

Command/Sync.hs

@@ -39,6 +39,7 @@ def = [command "sync" (paramOptional (paramRepeating paramRemote))
 -- syncing involves several operations, any of which can independently fail
 seek :: CommandSeek
 seek rs = do
+	prepMerge
 	branch <- fromMaybe nobranch <$> inRepo Git.Branch.current
 	remotes <- syncRemotes rs
 	return $ concat
@@ -52,6 +53,11 @@ seek rs = do
   where
 	nobranch = error "no branch is checked out"
 
+{- Merging may delete the current directory, so go to the top
+ - of the repo. -}
+prepMerge :: Annex ()
+prepMerge = liftIO . setCurrentDirectory =<< fromRepo Git.repoPath
+
 syncBranch :: Git.Ref -> Git.Ref
 syncBranch = Git.Ref.under "refs/heads/synced/"