From adda6c10882b4bd289d1e1cedfaf9ee78eab8871 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Wed, 9 Aug 2023 13:30:43 -0400
Subject: [PATCH] Add git-annex remote refs that are not newer to the merged
 refs list

Significant startup speed increase by avoiding repeatedly checking if some
remote git-annex branch refs need to be merged when it is not newer.

One way this could happen is when there are 2 remotes that are themselves
connected. The git-annex branch on the first remote gets updated. Then the
second remote pulls from the first, and merges in its git-annex branch.
Then the local repo pulls from the second remote, and merges its git-annex
branch. At this point, a pull from the first remote will get a git-annex
branch that is not newer, but is not on the merged refs list.

In my big repo, git-annex startup time dropped from 4 seconds to 0.1 seconds.
There were 5 to 10 such remote refs out of 18 remotes.

Sponsored-by: Graham Spencer on Patreon
---
 Annex/Branch.hs  | 12 +++++++-----
 CHANGELOG        |  2 ++
 Utility/Monad.hs |  8 ++++++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/Annex/Branch.hs b/Annex/Branch.hs
index ab4b43df3c..dce16667d7 100644
--- a/Annex/Branch.hs
+++ b/Annex/Branch.hs
@@ -183,23 +183,24 @@ updateTo' pairs = do
 	branchref <- getBranch
 	ignoredrefs <- getIgnoredRefs
 	let unignoredrefs = excludeset ignoredrefs pairs
-	tomerge <- if null unignoredrefs
-		then return []
+	(tomerge, notnewer) <- if null unignoredrefs
+		then return ([], [])
 		else do
 			mergedrefs <- getMergedRefs
-			filterM isnewer (excludeset mergedrefs unignoredrefs)
+			partitionM isnewer $
+				excludeset mergedrefs unignoredrefs
 	{- In a read-only repository, catching permission denied lets
 	 - query operations still work, although they will need to do
 	 - additional work since the refs are not merged. -}
 	catchPermissionDenied
 		(const (updatefailedperms tomerge))
-		(go branchref tomerge)
+		(go branchref tomerge notnewer)
   where
 	excludeset s = filter (\(r, _) -> S.notMember r s)
 
 	isnewer (r, _) = inRepo $ Git.Branch.changed fullname r
 
-	go branchref tomerge = do
+	go branchref tomerge notnewer = do
 		dirty <- journalDirty gitAnnexJournalDir
 		journalcleaned <- if null tomerge
 			{- Even when no refs need to be merged, the index
@@ -229,6 +230,7 @@ updateTo' pairs = do
 		journalclean <- if journalcleaned
 			then not <$> privateUUIDsKnown
 			else pure False
+		addMergedRefs notnewer
 		return $ UpdateMade
 			{ refsWereMerged = not (null tomerge)
 			, journalClean = journalclean 
diff --git a/CHANGELOG b/CHANGELOG
index 9dccfb1730..d1e28a8fb0 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -2,6 +2,8 @@ git-annex (10.20230803) UNRELEASED; urgency=medium
 
   * Fix behavior of onlyingroup.
   * info: Added --dead-repositories option. 
+  * Significant startup speed increase by avoiding repeatedly checking
+    if some remote git-annex branch refs need to be merged.
 
  -- Joey Hess <id@joeyh.name>  Mon, 07 Aug 2023 13:04:13 -0400
 
diff --git a/Utility/Monad.hs b/Utility/Monad.hs
index abe06f335c..6cd2c5e657 100644
--- a/Utility/Monad.hs
+++ b/Utility/Monad.hs
@@ -12,6 +12,7 @@ module Utility.Monad (
 	getM,
 	anyM,
 	allM,
+	partitionM,
 	untilTrue,
 	ifM,
 	(<||>),
@@ -45,6 +46,13 @@ allM :: Monad m => (a -> m Bool) -> [a] -> m Bool
 allM _ [] = return True
 allM p (x:xs) = p x <&&> allM p xs
 
+partitionM :: Monad m => (a -> m Bool) -> [a] -> m ([a], [a])
+partitionM _ [] = return ([], [])
+partitionM p (x:xs) = do
+	r <- p x
+	(as, bs) <- partitionM p xs
+	return $ if r then (x:as, bs) else (as, x:bs)
+
 {- Runs an action on values from a list until it succeeds. -}
 untilTrue :: Monad m => [a] -> (a -> m Bool) -> m Bool
 untilTrue = flip anyM