post-receive hook updateInstead emulation cleanup

The code is only needed because for a long time, git-annex didn't
install hooks in repos on crippled filesystems. Now it does, and they
work at least on FAT (where all files are executable) and Windows.

It would be possible to remove this code in v8 simply by re-installing
the hooks.

Command/Sync.hs

@@ -458,8 +458,9 @@ pushRemote o remote (Just branch, _) = stopUnless (pure (pushOption o) <&&> need
 		| remoteAnnexReadOnly gc = return False
 		| not (remoteAnnexPush gc) = return False
 		| otherwise = anyM (newer remote) [syncBranch branch, Annex.Branch.name]
-	-- Do updateInstead emulation for remotes on eg removable drives
-	-- formatted FAT, where the post-receive hook won't run.
+	-- Older remotes on crippled filesystems may not have a
+	-- post-receive hook set up, so when updateInstead emulation
+	-- is needed, run post-receive manually.
 	postpushupdate repo = case Git.repoWorkTree repo of
 		Nothing -> return True
 		Just wt -> ifM needemulation

doc/git-annex-post-receive.mdwn

@@ -13,7 +13,7 @@ automatically creates a post-receive hook using this.
 
 When a repository is configured with receive.denyCurrentBranch=updateInstead,
 pushes to the repository update its work tree. However, that does not work
-for repositories that use have an adjusted branch checked
+for repositories that have an adjusted branch checked
 out. The hook updates the work tree when run in such a repository,
 the same as running `git-annex merge` would.