Fix build with persistent-2.10.

Added an additional constraint that persistent needs.
This also builds with persistent-2.9.2 without needing any cpp.

CHANGELOG

@@ -11,6 +11,7 @@ git-annex (7.20191011) UNRELEASED; urgency=medium
     when they become empty, further reducing the size of the git-annex branch.
   * OSX: Deal with symbolic link problem that caused git to not be included in
     the git-annex.dmg.
+  * Fix build with persistent-2.10.
 
  -- Joey Hess <id@joeyh.name>  Thu, 19 Sep 2019 11:11:19 -0400
 

Database/Handle.hs

@@ -244,10 +244,15 @@ runSqliteRobustly tablename db a = do
 
 -- Like withSqlConn, but more robust.
 withSqlConnRobustly
-	 :: (MonadUnliftIO m, MonadLogger m, IsPersistBackend backend, BaseBackend backend ~ SqlBackend)
-	 => (LogFunc -> IO backend)
-	 -> (backend -> m a)
-	 -> m a
+	:: (MonadUnliftIO m
+		, MonadLogger m
+		, IsPersistBackend backend
+		, BaseBackend backend ~ SqlBackend
+		, BackendCompatible SqlBackend backend
+	    )
+	=> (LogFunc -> IO backend)
+	-> (backend -> m a)
+	-> m a
 withSqlConnRobustly open f = do
 	logFunc <- askLogFunc
 	withRunInIO $ \run -> bracket
@@ -258,8 +263,11 @@ withSqlConnRobustly open f = do
 -- Sqlite can throw ErrorBusy while closing a database; this catches
 -- the exception and retries.
 closeRobustly
-	 :: (IsPersistBackend backend, BaseBackend backend ~ SqlBackend)
-	 => backend
+	:: (IsPersistBackend backend
+		, BaseBackend backend ~ SqlBackend
+		, BackendCompatible SqlBackend backend
+	   )
+	=> backend
 	-> IO ()
 closeRobustly conn = go maxretries briefdelay
   where

doc/bugs/build_failure_on_macOS_10.14.6.mdwn

@@ -71,3 +71,5 @@ The Glorious Glasgow Haskell Compilation System, version 8.6.5
 ### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
 
 git-annex has been awesome for managing a massive collection of raw images and video clips across several storage targets and editing systems.
+
+> [[fixed|done]] --[[Joey]]

doc/bugs/build_failure_on_macOS_10.14.6/comment_2_da885d7d887035852d325a7427eba69e._comment

@@ -0,0 +1,26 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 2"""
+ date="2019-10-17T15:04:29Z"
+ content="""
+Thank you for maintaining the homebrew build, and for tracking down the
+persistent version.
+
+I've fixed this now, and will be making a new git-annex release today.
+
+FWIW, git-annex.cabal intentionally doesn't pin higher bounds of library
+versions. My thinking is that people who want a build pinned at known
+working versions should use stack to build, while people who are building
+with cabal tend to be the kind of people who are integrating git-annex with
+a larger system, and will probably want to build with whatever library
+versions shipped with their system (eg in a linux distribution), or
+with the latest and greatest.
+
+That does mean that everyone building with cabal is likely to run into this
+kind of breakage now and then, rather than me not noticing it until I update
+the pinned versions. Kind of offloading a bit of the work from me onto users,
+I have to admit.
+
+You can of course patch git-annex.cabal to use an older version if
+necessary.
+"""]]