From 583b8394b3c8f02a096352c76c63580c117d4482 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Fri, 3 Jun 2016 13:48:14 -0400
Subject: withAltRepo needs a separate queue of changes

The queue could potentially contain changes from before withAltRepo, and
get flushed inside the call, which would apply the changes to the modified
repo.

Or, changes could be queued in withAltRepo that were intended to affect
the modified repo, but don't get flushed until later.

I don't know of any cases where either happens, but better safe than sorry.

Note that this affect withIndexFile, which is used in git-annex branch
updates. So, it potentially makes things slower. Should not be by much;
the overhead consists only of querying the current queue a couple of times,
and potentially flushing changes queued within withAltRepo earlier, that
could have maybe been bundled with other later changes.

Notice in particular that the existing queue is not flushed when calling
withAltRepo. So eg when git annex add needs to stage files in the index,
it will still bundle them together efficiently.
---
 Annex/GitOverlay.hs | 19 +++++++++++++++----
 Annex/Queue.hs      |  1 +
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/Annex/GitOverlay.hs b/Annex/GitOverlay.hs
index 2193b7449..1b7ceb2e2 100644
--- a/Annex/GitOverlay.hs
+++ b/Annex/GitOverlay.hs
@@ -15,6 +15,7 @@ import Git.Types
 import Git.Index
 import Git.Env
 import qualified Annex
+import qualified Annex.Queue
 
 {- Runs an action using a different git index file. -}
 withIndexFile :: FilePath -> Annex a -> Annex a
@@ -71,8 +72,18 @@ withAltRepo
 withAltRepo modrepo unmodrepo a = do
 	g <- gitRepo
 	g' <- liftIO $ modrepo g
-	r <- tryNonAsync $ do
-		Annex.changeState $ \s -> s { Annex.repo = g' }
+	q <- Annex.Queue.get
+	v <- tryNonAsync $ do
+		Annex.changeState $ \s -> s
+			{ Annex.repo = g'
+			-- Start a separate queue for any changes made
+			-- with the modified repo.
+			, Annex.repoqueue = Nothing
+			}
 		a
-	Annex.changeState $ \s -> s { Annex.repo = unmodrepo g (Annex.repo s) }
-	either E.throw return r
+	void $ tryNonAsync Annex.Queue.flush
+	Annex.changeState $ \s -> s
+		{ Annex.repo = unmodrepo g (Annex.repo s)
+		, Annex.repoqueue = Just q
+		}
+	either E.throw return v
diff --git a/Annex/Queue.hs b/Annex/Queue.hs
index 0e1b0f68c..9c22e75fd 100644
--- a/Annex/Queue.hs
+++ b/Annex/Queue.hs
@@ -13,6 +13,7 @@ module Annex.Queue (
 	flush,
 	flushWhenFull,
 	size,
+	get,
 	mergeFrom,
 ) where
 
-- 
cgit v1.2.3