sync in view branch updates the view branch

* sync: When run in a view branch, refresh the view branch to reflect any
    changes that have been made to the parent branch or metadata.

This is basically working, but probably needs some more work to deal with
all the edge cases of things sync does.

Sponsored-by: Lawrence Brogan on Patreon

Command/Sync.hs

@@ -1,7 +1,7 @@
 {- git-annex command
  -
  - Copyright 2011 Joachim Breitner <mail@joachim-breitner.de>
- - Copyright 2011-2021 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2023 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -59,10 +59,11 @@ import Annex.UUID
 import Logs.UUID
 import Logs.Export
 import Logs.PreferredContent
-import Logs.View (fromViewBranch)
+import Logs.View
 import Annex.AutoMerge
 import Annex.AdjustedBranch
 import Annex.AdjustedBranch.Merge
+import Annex.View
 import Annex.Ssh
 import Annex.BloomFilter
 import Annex.UpdateInstead
@@ -440,7 +441,6 @@ updateBranches (Just branch, madj) = do
 	-- to be updated, if the adjustment is not stable, and the usual
 	-- configuration does not update it.
 	case madj of
-		Nothing -> noop
 		Just adj -> do
 			let origbranch = branch
 			propigateAdjustedCommits origbranch adj
@@ -448,13 +448,27 @@ updateBranches (Just branch, madj) = do
 				annexAdjustedBranchRefresh <$> Annex.getGitConfig >>= \case
 					0 -> adjustedBranchRefreshFull adj origbranch
 					_ -> return ()
+		-- When in a view branch, update it to reflect any changes
+		-- of its parent branch or the metadata.
+		Nothing -> currentView >>= \case
+			Nothing -> noop
+			Just view -> updateView view >>= \case
+				Nothing -> noop
+				Just newcommit -> do
+					ok <- inRepo $ Git.Command.runBool
+						[ Param "merge"
+						, Param (Git.fromRef newcommit)
+						]
+					unless ok $
+						giveup $ "failed to update view"
 					
 	-- Update the sync branch to match the new state of the branch
 	inRepo $ updateBranch (syncBranch branch) branch
 
 updateBranch :: Git.Branch -> Git.Branch -> Git.Repo -> IO ()
 updateBranch syncbranch updateto g = 
-	unlessM go $ giveup $ "failed to update " ++ Git.fromRef syncbranch
+	unlessM go $
+		giveup $ "failed to update " ++ Git.fromRef syncbranch
   where
 	go = Git.Command.runBool
 		[ Param "branch"