sync: print a hint about receive.denyNonFastForwards when a push fails

Command/Sync.hs

@@ -184,7 +184,11 @@ pushRemote remote branch = go =<< needpush
 		showStart "push" (Remote.name remote)
 		next $ next $ do
 			showOutput
-			inRepo $ pushBranch remote branch
+			ok <- inRepo $ pushBranch remote branch
+			unless ok $ do
+				warning $ unwords [ "Pushing to " ++ Remote.name remote ++ " failed." ]
+				showNote "(non-fast-forward problems can be solved by setting receive.denyNonFastforwards to false in the remote's git config)"
+			return ok
 
 {- Pushes a regular branch like master to a remote. Also pushes the git-annex
  - branch.
@@ -211,6 +215,9 @@ pushRemote remote branch = go =<< needpush
  - But overwriting of data on synced/git-annex can happen, in a race.
  - The only difference caused by using a forced push in that case is that
  - the last repository to push wins the race, rather than the first to push.
+ -
+ - The sync push will fail to overwrite if receive.denyNonFastforwards is
+ - set on the remote.
  -}
 pushBranch :: Remote -> Git.Ref -> Git.Repo -> IO Bool
 pushBranch remote branch g = tryIO (directpush g) `after` syncpush g

doc/assistant/release_notes.mdwn

@@ -1,12 +1,3 @@
-## 4.20131025
-
-Note that all past versions of the assistant, when used to create a
-git repository on a ssh server, set up the repository in a way that
-prevents `git annex sync` from working (although the assistant can sync
-with it). To fix this misconfiguration, you can ssh to the server
-and run this command inside the bare git repository:
-`git config receive.denyNonFastforwards false`
-
 ## version 4.20131024
 
 This version fixes several different bugs that could cause the webapp to

doc/bugs/Windows_and_Linux_in_direct_mode_confuses_git.mdwn

@@ -377,3 +377,8 @@ $
 
 # End of transcript or log.
 """]]
+
+> Apparently `test.git` had `receive.denyNonFastForwards`
+> set to true, which prevents the forced pushing `git annex sync`
+> needs to do. I have made it print out a hint about this setting
+> when a push failes. [[done]] --[[Joey]]