webdav: Changed path used on webdav server for temporary files.

Done to avoid a "tmp" directory appearing in webdav exports.

Also affects non-export webdav remotes, so interrupted uploads using the
old path will not overwrite it. However, PUT is quite likely to be
implemented atomically on web servers anyway, so I doubt this will cause
problems.

CHANGELOG

@@ -16,6 +16,7 @@ git-annex (6.20170819) UNRELEASED; urgency=medium
     the file is not present.
   * webdav: Fix lack of url-escaping of filenames. Mostly impacted exports
     of filenames containing eg spaces.
+  * webdav: Changed path used on webdav server for temporary files.
 
  -- Joey Hess <id@joeyh.name>  Mon, 28 Aug 2017 12:20:59 -0400
 

Remote/WebDAV.hs

@@ -127,7 +127,7 @@ store _  (Just dav) = httpStorer $ \k reqbody -> liftIO $ goDAV dav $ do
 
 storeHelper :: DavHandle -> DavLocation -> DavLocation -> RequestBody -> DAVT IO ()
 storeHelper dav tmp dest reqbody = do
-	void $ mkColRecursive tmpDir
+	maybe noop (void . mkColRecursive) (locationParent tmp)
 	inLocation tmp $
 		putContentM' (contentType, reqbody)
 	finalizeStore dav tmp dest
@@ -257,8 +257,8 @@ testDav url (Just (u, p)) = do
 	test $ liftIO $ evalDAVT url $ do
 		prepDAV user pass
 		makeParentDirs
-		void $ mkColRecursive tmpDir
-		inLocation (tmpLocation "git-annex-test") $ do
+		void $ mkColRecursive "/"
+		inLocation (tmpLocation "test") $ do
 			putContentM (Nothing, L8.fromString "test")
 			delContentM
   where

Remote/WebDAV/DavLocation.hs

@@ -46,18 +46,15 @@ keyDir k = addTrailingPathSeparator $ hashdir </> keyFile k
 keyLocation :: Key -> DavLocation
 keyLocation k = keyDir k ++ keyFile k
 
+exportLocation :: ExportLocation -> DavLocation
+exportLocation (ExportLocation f) = f
+
 {- Where we store temporary data for a key as it's being uploaded. -}
 keyTmpLocation :: Key -> DavLocation
 keyTmpLocation = tmpLocation . keyFile
 
-exportLocation :: ExportLocation -> DavLocation
-exportLocation (ExportLocation f) = f
-
 tmpLocation :: FilePath -> DavLocation
-tmpLocation f = tmpDir </> f
-
-tmpDir :: DavLocation
-tmpDir = "tmp"
+tmpLocation f = "git-annex-webdav-tmp-" ++ f
 
 locationParent :: String -> Maybe String
 locationParent loc